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* posix-timers: Convert abuses of BUG_ON to WARN_ONFrederic Weisbecker2013-12-091-5/+5
| | | | | | | | | | | | | | | The posix cpu timers code makes a heavy use of BUG_ON() but none of these concern fatal issues that require to stop the machine. So let's just warn the user when some internal state slips out of our hands. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Kosaki Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Andrew Morton <akpm@linux-foundation.org>
* posix-timers: Remove remaining uses of tasklist_lockFrederic Weisbecker2013-12-091-32/+44
| | | | | | | | | | | | | | | | | | | The remaining uses of tasklist_lock were mostly about synchronizing against sighand modifications, getting coherent and safe group samples and also thread/process wide timers list handling. All of this is already safely synchronizable with the target's sighand lock. Let's use it on these places instead. Also update the comments about locking. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Kosaki Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Andrew Morton <akpm@linux-foundation.org>
* posix-timers: Use sighand lock instead of tasklist_lock on timer deletionFrederic Weisbecker2013-12-091-6/+11
| | | | | | | | | | | | | | | | | | | | | | | | | | Timer deletion doesn't need the tasklist lock. We need to protect against: * concurrent access to the lists p->cputime_expires and p->sighand->cputime_expires * task reaping that may also delete the timer list entry * timer firing We already hold the timer lock which protects us against concurrent timer firing. The rest only need the targets sighand to be locked. So hold it and drop the use of tasklist_lock there. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Kosaki Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Andrew Morton <akpm@linux-foundation.org>
* posix-timers: Use sighand lock instead of tasklist_lock for task clock sampleFrederic Weisbecker2013-12-091-3/+13
| | | | | | | | | | | | | | | | | | | | | | | There is no need for the tasklist_lock just to take a process wide clock sample. All we need is to get a coherent sample that doesn't race with exit() and exec(): * exit() may be concurrently reaping a task and flushing its time * sighand is unstable under exit() and exec(), and the latter also result in group leader that can change To protect against these, locking the target's sighand is enough. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Kosaki Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Andrew Morton <akpm@linux-foundation.org>
* posix-timers: Consolidate posix_cpu_clock_get()Frederic Weisbecker2013-12-091-34/+30
| | | | | | | | | | | | | | | | | | | | | | | | | | Consolidate the clock sampling common code used for both local and remote targets. Note that this introduces a tiny user ABI change: if a PID is passed to clock_gettime() along the clockid, we used to forbid a process wide clock sample when that PID doesn't belong to a group leader. Now after this patch we allow process wide clock samples if that PID belongs to the current task, even if the current task is not the group leader. But local process wide clock samples are allowed if PID == 0 (current task) even if the current task is not the group leader. So in the end this should be no big deal as this actually harmonize the behaviour when the remote sample is actually a local one. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Kosaki Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Andrew Morton <akpm@linux-foundation.org>
* posix-timers: Remove useless clock sample on timers cleanupFrederic Weisbecker2013-12-091-23/+7
| | | | | | | | | | | | | | | | a0b2062b0904ef07944c4a6e4d0f88ee44f1e9f2 ("posix_timers: fix racy timer delta caching on task exit") forgot to remove the arguments used for timer caching. Fix this leftover. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Kosaki Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Andrew Morton <akpm@linux-foundation.org>
* posix-timers: Remove dead task special caseFrederic Weisbecker2013-12-091-45/+25
| | | | | | | | | | | | | | | | | Now that we've removed all the optimizations that could result in NULL timer's targets, we can remove all the associated special case handling. Also add some warnings on NULL targets to spot any possible leftover. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Kosaki Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Andrew Morton <akpm@linux-foundation.org>
* posix-timers: Cleanup reaped target handlingFrederic Weisbecker2013-12-091-6/+0
| | | | | | | | | | | | | | | | | | | | | | When a timer's target is seen to be buried, for example on calls to timer_gettime(), the posix cpu timers code behaves a bit like a garbage collector and releases early the reference to the task. Then again, this optimization complicates the code for no much value: it's up to the user to release the timer and its associated ressources by calling timer_delete() after it buries the target tasks. Remove this to simplify the code. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Kosaki Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Andrew Morton <akpm@linux-foundation.org>
* posix-timers: Remove dead process posix cpu timers cachingFrederic Weisbecker2013-12-091-34/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Now that we removed dead thread posix cpu timers caching, lets remove the dead process wide version. This caching is similar to the per thread version but it should be even more rare: * If the process id dead, we are not reading its timers status from a thread belonging to its group since they are all dead. So this caching only concern remote process timers reads. Now posix cpu timers using itimers or timer_settime() can't do remote process timers anyway so it's not even clear if there is actually a user for this caching. * Unlike per thread timers caching, this only applies to zombies targets. Buried targets' process wide timers return 0 values. But then again, timer_gettime() can't read remote process timers, so if the process is dead, there can't be any reader left anyway. Then again this caching seem to complicate the code for corner cases that are probably not worth it. So lets get rid of it. Also remove the sample snapshot on dying process timer that is now useless, as suggested by Kosaki. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Kosaki Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Andrew Morton <akpm@linux-foundation.org>
* posix-timers: Remove dead thread posix cpu timers cachingFrederic Weisbecker2013-12-091-18/+16
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | When a task is exiting or has exited, its posix cpu timers don't tick anymore and won't elapse further. It's too late for them to expire. So any further call to timer_gettime() on these timers will return the same remaining expiry time. The current code optimize this by caching the remaining delta and storing it where we use to save the absolute expiration time. This way, the future calls to timer_gettime() won't need to compute the difference between the absolute expiration time and the current time anymore. Now this optimization doesn't seem to bring much value. Computing the timer remaining delta is not very costly. Fetching the timer value OTOH can be costly in two ways: * CPUCLOCK_SCHED read requires to lock the target's rq. But some optimizations are on the way to make task_sched_runtime() not holding the rq lock of a non-running target. * CPUCLOCK_VIRT/CPUCLOCK_PROF read simply consist in fetching current->utime/current->stime except when the system uses full dynticks cputime accounting. The latter requires a per task lock in order to correctly compute user and system time. But once the target is dead, this lock shouldn't be contended anyway. All in one this caching doesn't seem to be justified. Given that it complicates the code significantly for few wins, let's remove it on single thread timers. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Kosaki Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Andrew Morton <akpm@linux-foundation.org>
* posix-timers: Fix full dynticks CPUs kick on timer reschedulingFrederic Weisbecker2013-12-021-11/+7
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | A posix CPU timer can be rearmed while it is firing or after it is notified with a signal. This can happen for example with timers that were set with a non zero interval in timer_settime(). This rearming can happen in two places: 1) On timer firing time, which happens on the target's tick. If the timer can't trigger a signal because it is ignored, it reschedules itself to honour the timer interval. 2) On signal handling from the timer's notification target. This one can be a different task than the timer's target itself. Once the signal is notified, the notification target rearms the timer, again to honour the timer interval. When a timer is rearmed, we need to notify the full dynticks CPUs such that they restart their tick in case they are running tasks that may have a share in elapsing this timer. Now the 1st case above handles full dynticks CPUs with a call to posix_cpu_timer_kick_nohz() from the posix cpu timer firing code. But the second case ignores the fact that some CPUs may run non-idle tasks with their tick off. As a result, when a timer is resheduled after its signal notification, the full dynticks CPUs may completely ignore it and not tick on the timer as expected This patch fixes this bug by handling both cases in one. All we need is to move the kick to the rearming common code in posix_cpu_timer_schedule(). Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Olivier Langlois <olivier@olivierlanglois.net>
* posix-timers: Spare workqueue if there is no full dynticks CPU to kickFrederic Weisbecker2013-12-021-1/+2
| | | | | | | | | | | | | | | | | | | | | | | After a posix cpu timer is set, a workqueue is scheduled in order to kick the full dynticks CPUs and let them restart their tick if necessary in case the task they are running is concerned by the new timer. This kick is implemented by way of IPIs, which require interrupts to be enabled, hence the need for a workqueue to raise them because the posix cpu timer set path has interrupts disabled. Now if there is no full dynticks CPU on the system, the workqueue is still scheduled but it simply won't send any IPI and return immediately. So lets spare that worqueue when it is not needed. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Steven Rostedt <rostedt@goodmis.org>
* posix_timers: fix racy timer delta caching on task exitFrederic Weisbecker2013-07-031-11/+11
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | When a task exits, we perform a caching of the remaining cputime delta before expiring of its timers. This is done from the following places: * When the task is reaped. We iterate through its list of posix cpu timers and store the remaining timer delta to the timer struct instead of the absolute value. (See posix_cpu_timers_exit() / posix_cpu_timers_exit_group() ) * When we call posix_cpu_timer_get() or posix_cpu_timer_schedule(). If the timer's task is considered dying when watched from these places, the same conversion from absolute to relative expiry time is performed. Then the given task's reference is released. (See clear_dead_task() ). The relevance of this caching is questionable but this is another and deeper debate. The big issue here is that these two sources of caching don't mix up very well together. More specifically, the caching can easily be done twice, resulting in a wrong delta as it gets spuriously substracted a second time by the elapsed clock. This can happen in the following scenario: 1) The task exits and gets reaped: we call posix_cpu_timers_exit() and the absolute timer expiry values are converted to a relative delta. 2) timer_gettime() -> posix_cpu_timer_get() is called and relies on clear_dead_task() because tsk->exit_state == EXIT_DEAD. The delta gets substracted again by the elapsed clock and we return a wrong result. To fix this, just remove the caching done on task reaping time. It doesn't bring much value on its own. The caching done from posix_cpu_timer_get/schedule is enough. And it would also be hard to get it really right: we could make it put and clear the target task in the timer struct so that readers know if they are dealing with a relative cached of absolute value. But it would be racy. The only safe way to do it would be to lock the itimer->it_lock so that we know nobody reads the cputime expiry value while we modify it and its target task reference. Doing so would involve some funny workarounds to avoid circular lock against the sighand lock. There is just no reason to maintain this. The user visible effect of this patch can be observed by running the following code: it creates a subthread that launches a posix cputimer which expires after 10 seconds. But then the subthread only busy loops for 2 seconds and exits. The parent reaps the subthread and read the timer value. Its expected value should the be the initial timer's expiration value minus the cputime elapsed in the subthread. Roughly 10 - 2 = 8 seconds: #include <sys/time.h> #include <stdio.h> #include <unistd.h> #include <time.h> #include <pthread.h> static timer_t id; static struct itimerspec val = { .it_value.tv_sec = 10, }, new; static void *thread(void *unused) { int err; struct timeval start, end, diff; timer_create(CLOCK_THREAD_CPUTIME_ID, NULL, &id); if (err < 0) { perror("Can't create timer\n"); return NULL; } /* Arm 10 sec timer */ err = timer_settime(id, 0, &val, NULL); if (err < 0) { perror("Can't set timer\n"); return NULL; } /* Exit after 2 seconds of execution */ gettimeofday(&start, NULL); do { gettimeofday(&end, NULL); timersub(&end, &start, &diff); } while (diff.tv_sec < 2); return NULL; } int main(int argc, char **argv) { pthread_t pthread; int err; err = pthread_create(&pthread, NULL, thread, NULL); if (err) { perror("Can't create thread\n"); return -1; } pthread_join(pthread, NULL); /* Just wait a little bit to make sure the child got reaped */ sleep(1); err = timer_gettime(id, &new); if (err) perror("Can't get timer value\n"); printf("%d %ld\n", new.it_value.tv_sec, new.it_value.tv_nsec); return 0; } Before the patch: $ ./posix_cpu_timers 6 2278074 After the patch: $ ./posix_cpu_timers 8 1158766 Before the patch, the elapsed time got two more seconds spuriously accounted. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Stanislaw Gruszka <sgruszka@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Ingo Molnar <mingo@elte.hu> Cc: Oleg Nesterov <oleg@redhat.com> Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com> Cc: Olivier Langlois <olivier@trillion01.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* posix-timers: correctly get dying task time sample in posix_cpu_timer_schedule()Frederic Weisbecker2013-07-031-0/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | In order to re-arm a timer after it fired, we take a sample of the current process or thread cputime. If the task is dying though, we don't arm anything but we cache the remaining timer expiration delta for further reads. Something similar is performed in posix_cpu_timer_get() but here we forget to take the process wide cputime sample before caching it. As a result we are storing random stack content, leading every further reads of that timer to return junk values. Fix this by taking the appropriate sample in the case of process wide timers. This probably doesn't matter much in practice because, at this stage, the thread is the last one in the group and we reached exit_notify(). This implies that we called exit_itimers() and there should be no more timers to handle for that task. So this is likely dead code anyway but let's fix the current logic and the warning that came along: kernel/posix-cpu-timers.c: In function 'posix_cpu_timer_schedule': kernel/posix-cpu-timers.c:1127: warning: 'now' may be used uninitialized in this function Then we can start to think further about cleaning up that code. Reported-by: Andrew Morton <akpm@linux-foundation.org> Reported-by: Chen Gang <gang.chen@asianux.com> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Stanislaw Gruszka <sgruszka@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Ingo Molnar <mingo@elte.hu> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Chen Gang <gang.chen@asianux.com> Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com> Cc: Olivier Langlois <olivier@trillion01.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* posix_cpu_timers: consolidate expired timers checkFrederic Weisbecker2013-07-031-85/+33
| | | | | | | | | | | | | | | | | | Consolidate the common code amongst per thread and per process timers list on tick time. List traversal, expiry check and subsequent updates can be shared in a common helper. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Stanislaw Gruszka <sgruszka@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Ingo Molnar <mingo@elte.hu> Cc: Oleg Nesterov <oleg@redhat.com> Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com> Cc: Olivier Langlois <olivier@trillion01.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* posix_cpu_timers: consolidate timer list cleanupsFrederic Weisbecker2013-07-031-29/+19
| | | | | | | | | | | | | | | | | | Cleaning up the posix cpu timers on task exit shares some common code among timer list types, most notably the list traversal and expiry time update. Unify this in a common helper. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Stanislaw Gruszka <sgruszka@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Ingo Molnar <mingo@elte.hu> Cc: Oleg Nesterov <oleg@redhat.com> Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com> Cc: Olivier Langlois <olivier@trillion01.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* posix_cpu_timer: consolidate expiry time typeFrederic Weisbecker2013-07-031-160/+106
| | | | | | | | | | | | | | | | | | | | | | The posix cpu timer expiry time is stored in a union of two types: a 64 bits field if we rely on scheduler precise accounting, or a cputime_t if we rely on jiffies. This results in quite some duplicate code and special cases to handle the two types. Just unify this into a single 64 bits field. cputime_t can always fit into it. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Stanislaw Gruszka <sgruszka@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Ingo Molnar <mingo@elte.hu> Cc: Oleg Nesterov <oleg@redhat.com> Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com> Cc: Olivier Langlois <olivier@trillion01.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* posix_timers: Fix pre-condition to stop the tick on full dynticksFrederic Weisbecker2013-04-221-3/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | The test that checks if a CPU can stop its tick from posix CPU timers angle was mistakenly inverted. What we want is to prevent the tick from being stopped as long as the current CPU's task runs a posix CPU timer. Fix this. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Chris Metcalf <cmetcalf@tilera.com> Cc: Christoph Lameter <cl@linux.com> Cc: Geoff Levand <geoff@infradead.org> Cc: Gilad Ben Yossef <gilad@benyossef.com> Cc: Hakan Akkan <hakanakkan@gmail.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Kevin Hilman <khilman@linaro.org> Cc: Li Zhong <zhong@linux.vnet.ibm.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de>
* posix_timers: New API to prevent from stopping the tick when timers are runningFrederic Weisbecker2013-04-191-15/+26
| | | | | | | | | | | | | | | | | | | | | | Bring a new helper that the full dynticks infrastructure can call in order to know if it can safely stop the tick from the posix cpu timers subsystem point of view. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Chris Metcalf <cmetcalf@tilera.com> Cc: Christoph Lameter <cl@linux.com> Cc: Geoff Levand <geoff@infradead.org> Cc: Gilad Ben Yossef <gilad@benyossef.com> Cc: Hakan Akkan <hakanakkan@gmail.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Kevin Hilman <khilman@linaro.org> Cc: Li Zhong <zhong@linux.vnet.ibm.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de>
* posix_timers: Kick full dynticks CPUs when a posix cpu timer is armedFrederic Weisbecker2013-04-191-1/+34
| | | | | | | | | | | | | | | | | | | | | | | | | Kick the full dynticks CPUs when a posix cpu timer is enqueued by way of a standard call to posix_cpu_timer_set() or set_process_cpu_timer(). This also include rescheduled firing timers. This way they can re-evaluate the state of (and possibly restart) their tick against the new expiry modification. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Chris Metcalf <cmetcalf@tilera.com> Cc: Christoph Lameter <cl@linux.com> Cc: Geoff Levand <geoff@infradead.org> Cc: Gilad Ben Yossef <gilad@benyossef.com> Cc: Hakan Akkan <hakanakkan@gmail.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Kevin Hilman <khilman@linaro.org> Cc: Li Zhong <zhong@linux.vnet.ibm.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de>
* Merge branch 'timers-core-for-linus' of ↵Linus Torvalds2013-02-191-2/+21
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull timer changes from Ingo Molnar: "Main changes: - ntp: Add CONFIG_RTC_SYSTOHC: a generic RTC driver facility complementing the existing CONFIG_RTC_HCTOSYS, which uses NTP to keep the hardware clock updated. - posix-timers: Fix clock_adjtime to always return timex data on success. This is changing the ABI, but no breakage was expected and found - caution is warranted nevertheless. - platform persistent clock improvements/cleanups. - clockevents: refactor timer broadcast handling to be more generic and less duplicated with matching architecture code (mostly ARM motivated.) - various fixes and cleanups" * 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: timers/x86/hpet: Use HPET_COUNTER to specify the hpet counter in vread_hpet() posix-cpu-timers: Fix nanosleep task_struct leak clockevents: Fix generic broadcast for FEAT_C3STOP time, Fix setting of hardware clock in NTP code hrtimer: Prevent hrtimer_enqueue_reprogram race clockevents: Add generic timer broadcast function clockevents: Add generic timer broadcast receiver timekeeping: Switch HAS_PERSISTENT_CLOCK to ALWAYS_USE_PERSISTENT_CLOCK x86/time/rtc: Don't print extended CMOS year when reading RTC x86: Select HAS_PERSISTENT_CLOCK on x86 timekeeping: Add CONFIG_HAS_PERSISTENT_CLOCK option rtc: Skip the suspend/resume handling if persistent clock exist timekeeping: Add persistent_clock_exist flag posix-timers: Fix clock_adjtime to always return timex data on success Round the calculated scale factor in set_cyc2ns_scale() NTP: Add a CONFIG_RTC_SYSTOHC configuration MAINTAINERS: Update John Stultz's email time: create __getnstimeofday for WARNless calls
| * posix-cpu-timers: Fix nanosleep task_struct leakStanislaw Gruszka2013-02-151-2/+21
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The trinity fuzzer triggered a task_struct reference leak via clock_nanosleep with CPU_TIMERs. do_cpu_nanosleep() calls posic_cpu_timer_create(), but misses a corresponding posix_cpu_timer_del() which leads to the task_struct reference leak. Reported-and-tested-by: Tommi Rantala <tt.rantala@gmail.com> Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com> Cc: Dave Jones <davej@redhat.com> Cc: John Stultz <john.stultz@linaro.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: stable@vger.kernel.org Link: http://lkml.kernel.org/r/20130215100810.GF4392@redhat.com Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
* | cputime: Use accessors to read task cputime statsFrederic Weisbecker2013-01-271-6/+22
|/ | | | | | | | | | | | | | | | | | | This is in preparation for the full dynticks feature. While remotely reading the cputime of a task running in a full dynticks CPU, we'll need to do some extra-computation. This way we can account the time it spent tickless in userspace since its last cputime snapshot. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Ingo Molnar <mingo@kernel.org> Cc: Li Zhong <zhong@linux.vnet.ibm.com> Cc: Namhyung Kim <namhyung.kim@lge.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de>
* Merge tag 'random_for_linus' of ↵Linus Torvalds2012-12-191-0/+3
|\ | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/tytso/random Pull random updates from Ted Ts'o: "A few /dev/random improvements for the v3.8 merge window." * tag 'random_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/random: random: Mix cputime from each thread that exits to the pool random: prime last_data value per fips requirements random: fix debug format strings random: make it possible to enable debugging without rebuild
| * random: Mix cputime from each thread that exits to the poolNick Kossifidis2012-12-161-0/+3
| | | | | | | | | | | | | | | | | | | | When a thread exits mix it's cputime (userspace + kernelspace) to the entropy pool. We don't know how "random" this is, so we use add_device_randomness that doesn't mess with entropy count. Signed-off-by: Nick Kossifidis <mickflemm@gmail.com> Signed-off-by: Theodore Ts'o <tytso@mit.edu>
* | cputime: Move thread_group_cputime() to sched codeFrederic Weisbecker2012-11-281-24/+0
|/ | | | | | | | | | | | thread_group_cputime() is a general cputime API that is not only used by posix cpu timer. Let's move this helper to sched code. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
* [S390] cputime: add sparse checking and cleanupMartin Schwidefsky2011-12-151-80/+52
| | | | | | | | Make cputime_t and cputime64_t nocast to enable sparse checking to detect incorrect use of cputime. Drop the cputime macros for simple scalar operations. The conversion macros are still needed. Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
* Merge branch 'core-locking-for-linus' of ↵Linus Torvalds2011-10-261-7/+7
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip * 'core-locking-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (27 commits) rtmutex: Add missing rcu_read_unlock() in debug_rt_mutex_print_deadlock() lockdep: Comment all warnings lib: atomic64: Change the type of local lock to raw_spinlock_t locking, lib/atomic64: Annotate atomic64_lock::lock as raw locking, x86, iommu: Annotate qi->q_lock as raw locking, x86, iommu: Annotate irq_2_ir_lock as raw locking, x86, iommu: Annotate iommu->register_lock as raw locking, dma, ipu: Annotate bank_lock as raw locking, ARM: Annotate low level hw locks as raw locking, drivers/dca: Annotate dca_lock as raw locking, powerpc: Annotate uic->lock as raw locking, x86: mce: Annotate cmci_discover_lock as raw locking, ACPI: Annotate c3_lock as raw locking, oprofile: Annotate oprofilefs lock as raw locking, video: Annotate vga console lock as raw locking, latencytop: Annotate latency_lock as raw locking, timer_stats: Annotate table_lock as raw locking, rwsem: Annotate inner lock as raw locking, semaphores: Annotate inner lock as raw locking, sched: Annotate thread_group_cputimer as raw ... Fix up conflicts in kernel/posix-cpu-timers.c manually: making cputimer->cputime a raw lock conflicted with the ABBA fix in commit bcd5cff7216f ("cputimer: Cure lock inversion").
| * locking, sched: Annotate thread_group_cputimer as rawThomas Gleixner2011-09-131-6/+6
| | | | | | | | | | | | | | | | | | | | | | | | The thread_group_cputimer lock can be taken in atomic context and therefore cannot be preempted on -rt - annotate it. In mainline this change documents the low level nature of the lock - otherwise there's no functional difference. Lockdep and Sparse checking will work as usual. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* | cputimer: Cure lock inversionPeter Zijlstra2011-10-181-3/+4
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | There's a lock inversion between the cputimer->lock and rq->lock; notably the two callchains involved are: update_rlimit_cpu() sighand->siglock set_process_cpu_timer() cpu_timer_sample_group() thread_group_cputimer() cputimer->lock thread_group_cputime() task_sched_runtime() ->pi_lock rq->lock scheduler_tick() rq->lock task_tick_fair() update_curr() account_group_exec() cputimer->lock Where the first one is enabling a CLOCK_PROCESS_CPUTIME_ID timer, and the second one is keeping up-to-date. This problem was introduced by e8abccb7193 ("posix-cpu-timers: Cure SMP accounting oddities"). Cure the problem by removing the cputimer->lock and rq->lock nesting, this leaves concurrent enablers doing duplicate work, but the time wasted should be on the same order otherwise wasted spinning on the lock and the greater-than assignment filter should ensure we preserve monotonicity. Reported-by: Dave Jones <davej@redhat.com> Reported-by: Simon Kirby <sim@hostway.ca> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: stable@kernel.org Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Link: http://lkml.kernel.org/r/1318928713.21167.4.camel@twins Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
* | posix-cpu-timers: Cure SMP wobblesPeter Zijlstra2011-09-301-2/+3
|/ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | David reported: Attached below is a watered-down version of rt/tst-cpuclock2.c from GLIBC. Just build it with "gcc -o test test.c -lpthread -lrt" or similar. Run it several times, and you will see cases where the main thread will measure a process clock difference before and after the nanosleep which is smaller than the cpu-burner thread's individual thread clock difference. This doesn't make any sense since the cpu-burner thread is part of the top-level process's thread group. I've reproduced this on both x86-64 and sparc64 (using both 32-bit and 64-bit binaries). For example: [davem@boricha build-x86_64-linux]$ ./test process: before(0.001221967) after(0.498624371) diff(497402404) thread: before(0.000081692) after(0.498316431) diff(498234739) self: before(0.001223521) after(0.001240219) diff(16698) [davem@boricha build-x86_64-linux]$ The diff of 'process' should always be >= the diff of 'thread'. I make sure to wrap the 'thread' clock measurements the most tightly around the nanosleep() call, and that the 'process' clock measurements are the outer-most ones. --- #include <unistd.h> #include <stdio.h> #include <stdlib.h> #include <time.h> #include <fcntl.h> #include <string.h> #include <errno.h> #include <pthread.h> static pthread_barrier_t barrier; static void *chew_cpu(void *arg) { pthread_barrier_wait(&barrier); while (1) __asm__ __volatile__("" : : : "memory"); return NULL; } int main(void) { clockid_t process_clock, my_thread_clock, th_clock; struct timespec process_before, process_after; struct timespec me_before, me_after; struct timespec th_before, th_after; struct timespec sleeptime; unsigned long diff; pthread_t th; int err; err = clock_getcpuclockid(0, &process_clock); if (err) return 1; err = pthread_getcpuclockid(pthread_self(), &my_thread_clock); if (err) return 1; pthread_barrier_init(&barrier, NULL, 2); err = pthread_create(&th, NULL, chew_cpu, NULL); if (err) return 1; err = pthread_getcpuclockid(th, &th_clock); if (err) return 1; pthread_barrier_wait(&barrier); err = clock_gettime(process_clock, &process_before); if (err) return 1; err = clock_gettime(my_thread_clock, &me_before); if (err) return 1; err = clock_gettime(th_clock, &th_before); if (err) return 1; sleeptime.tv_sec = 0; sleeptime.tv_nsec = 500000000; nanosleep(&sleeptime, NULL); err = clock_gettime(th_clock, &th_after); if (err) return 1; err = clock_gettime(my_thread_clock, &me_after); if (err) return 1; err = clock_gettime(process_clock, &process_after); if (err) return 1; diff = process_after.tv_nsec - process_before.tv_nsec; printf("process: before(%lu.%.9lu) after(%lu.%.9lu) diff(%lu)\n", process_before.tv_sec, process_before.tv_nsec, process_after.tv_sec, process_after.tv_nsec, diff); diff = th_after.tv_nsec - th_before.tv_nsec; printf("thread: before(%lu.%.9lu) after(%lu.%.9lu) diff(%lu)\n", th_before.tv_sec, th_before.tv_nsec, th_after.tv_sec, th_after.tv_nsec, diff); diff = me_after.tv_nsec - me_before.tv_nsec; printf("self: before(%lu.%.9lu) after(%lu.%.9lu) diff(%lu)\n", me_before.tv_sec, me_before.tv_nsec, me_after.tv_sec, me_after.tv_nsec, diff); return 0; } This is due to us using p->se.sum_exec_runtime in thread_group_cputime() where we iterate the thread group and sum all data. This does not take time since the last schedule operation (tick or otherwise) into account. We can cure this by using task_sched_runtime() at the cost of having to take locks. This also means we can (and must) do away with thread_group_sched_runtime() since the modified thread_group_cputime() is now more accurate and would deadlock when called from thread_group_sched_runtime(). Aside of that it makes the function safe on 32 bit systems. The old code added t->se.sum_exec_runtime unprotected. sum_exec_runtime is a 64bit value and could be changed on another cpu at the same time. Reported-by: David Miller <davem@davemloft.net> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: stable@kernel.org Link: http://lkml.kernel.org/r/1314874459.7945.22.camel@twins Tested-by: David Miller <davem@davemloft.net> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
* hrtimers: Avoid touching inactive timer basesThomas Gleixner2011-05-231-2/+2
| | | | | | | | Instead of iterating over all possible timer bases avoid it by marking the active bases in the cpu base. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Peter Zijlstra <peterz@infradead.org>
* Fix common misspellingsLucas De Marchi2011-03-311-1/+1
| | | | | | Fixes generated by 'codespell' and manually reviewed. Signed-off-by: Lucas De Marchi <lucas.demarchi@profusion.mobi>
* posix-timers: Cleanup namespaceThomas Gleixner2011-02-021-2/+2
| | | | | | | | | | | | Rename register_posix_clock() to posix_timers_register_clock(). That's what the function really does. As a side effect this cleans up the posix_clock namespace for the upcoming dynamic posix_clock infrastructure. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Tested-by: Richard Cochran <richard.cochran@omicron.at> Cc: John Stultz <johnstul@us.ibm.com> LKML-Reference: <alpine.LFD.2.00.1102021222240.31804@localhost6.localdomain6>
* posix-timers: Make posix-cpu-timers functions staticThomas Gleixner2011-02-021-12/+15
| | | | | | | | | All functions are accessed via clock_posix_cpu now. So make them static. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: John Stultz <johnstul@us.ibm.com> Tested-by: Richard Cochran <richard.cochran@omicron.at> LKML-Reference: <20110201134419.389755466@linutronix.de>
* posix-timers: Convert clock_settime to clockid_to_kclock()Thomas Gleixner2011-02-021-2/+0
| | | | | | | | | | | Use the new kclock decoding function in clock_settime and cleanup all kclocks which use the default functions. Rename the misnomed common_clock_set() to posix_clock_realtime_set(). Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: John Stultz <johnstul@us.ibm.com> Tested-by: Richard Cochran <richard.cochran@omicron.at> LKML-Reference: <20110201134418.518851246@linutronix.de>
* posix-cpu-timers: Remove the stub nanosleep functionsThomas Gleixner2011-02-021-11/+0
| | | | | | | | | | | | | | CLOCK_THREAD_CPUTIME_ID implements stub functions for nanosleep and nanosleep_restart, which return -EINVAL. That return value is wrong. The correct return value is -ENOTSUP. Remove the stubs and let the new dispatch code return the correct error code. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: John Stultz <johnstul@us.ibm.com> Tested-by: Richard Cochran <richard.cochran@omicron.at> LKML-Reference: <20110201134418.422446502@linutronix.de>
* posix-timers: Cleanup restart_block usageThomas Gleixner2011-02-021-23/+15
| | | | | | | | | | posix timers still use the legacy arg0-arg3 members of restart_block. Use restart_block.nanosleep instead Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: John Stultz <johnstul@us.ibm.com> Tested-by: Richard Cochran <richard.cochran@omicron.at> LKML-Reference: <20110201134418.232288779@linutronix.de>
* posix-timers: Introduce clock_posix_cpuThomas Gleixner2011-02-021-0/+12
| | | | | | | | | | | | | | | | | The CLOCK_DISPATCH() macro is a horrible magic. We call common functions if a function pointer is not set. That's just backwards. To support dynamic file decriptor based clocks we need to cleanup that dispatch logic. Create a k_clock struct clock_posix_cpu which has all the posix-cpu-timer functions filled in. After the cleanup the functions can be made static. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: John Stultz <johnstul@us.ibm.com> Tested-by: Richard Cochran <richard.cochran@omicron.at> LKML-Reference: <20110201134417.841974553@linutronix.de>
* posix-timers: Cleanup struct initializersThomas Gleixner2011-02-021-12/+12
| | | | | | | | | Cosmetic. No functional change Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: John Stultz <johnstul@us.ibm.com> Tested-by: Richard Cochran <richard.cochran@omicron.at> LKML-Reference: <20110201134417.745627057@linutronix.de>
* posix-cpu-timers: Rcu_read_lock/unlock protect find_task_by_vpid callSergey Senozhatsky2010-11-101-6/+6
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Commit 4221a9918e38b7494cee341dda7b7b4bb8c04bde "Add RCU check for find_task_by_vpid()" introduced rcu_lockdep_assert to find_task_by_pid_ns. Add rcu_read_lock/rcu_read_unlock to call find_task_by_vpid. Tetsuo Handa wrote: | Quoting from one of posts in that thead | http://kerneltrap.org/mailarchive/linux-kernel/2010/2/8/4536388 | || Usually tasklist gives enough protection, but if copy_process() fails || it calls free_pid() lockless and does call_rcu(delayed_put_pid(). || This means, without rcu lock find_pid_ns() can't scan the hash table || safely. Thomas Gleixner wrote: | We can remove the tasklist_lock while at it. rcu_read_lock is enough. Patch also replaces thread_group_leader with has_group_leader_pid in accordance to comment by Oleg Nesterov: | ... thread_group_leader() check is not relaible without | tasklist. If we race with de_thread() find_task_by_vpid() can find | the new leader before it updates its ->group_leader. | | perhaps it makes sense to change posix_cpu_timer_create() to use | has_group_leader_pid() instead, just to make this code not look racy | and avoid adding new problems. Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Stanislaw Gruszka <sgruszka@redhat.com> Reviewed-by: Oleg Nesterov <oleg@redhat.com> LKML-Reference: <20101103165256.GD30053@swordfish.minsk.epam.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
* Merge branch 'writable_limits' of git://decibel.fi.muni.cz/~xslaby/linuxLinus Torvalds2010-08-101-4/+4
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | * 'writable_limits' of git://decibel.fi.muni.cz/~xslaby/linux: unistd: add __NR_prlimit64 syscall numbers rlimits: implement prlimit64 syscall rlimits: switch more rlimit syscalls to do_prlimit rlimits: redo do_setrlimit to more generic do_prlimit rlimits: add rlimit64 structure rlimits: do security check under task_lock rlimits: allow setrlimit to non-current tasks rlimits: split sys_setrlimit rlimits: selinux, do rlimits changes under task_lock rlimits: make sure ->rlim_max never grows in sys_setrlimit rlimits: add task_struct to update_rlimit_cpu rlimits: security, add task_struct to setrlimit Fix up various system call number conflicts. We not only added fanotify system calls in the meantime, but asm-generic/unistd.h added a wait4 along with a range of reserved per-architecture system calls.
| * rlimits: add task_struct to update_rlimit_cpuJiri Slaby2010-07-161-4/+4
| | | | | | | | | | | | | | | | Add task_struct as a parameter to update_rlimit_cpu to be able to set rlimit_cpu of different task than current. Signed-off-by: Jiri Slaby <jirislaby@gmail.com> Acked-by: James Morris <jmorris@namei.org>
* | sched: Fix the racy usage of thread_group_cputimer() in fastpath_timer_check()Oleg Nesterov2010-06-181-1/+4
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | fastpath_timer_check()->thread_group_cputimer() is racy and unneeded. It is racy because another thread can clear ->running before thread_group_cputimer() takes cputimer->lock. In this case thread_group_cputimer() will set ->running = true again and call thread_group_cputime(). But since we do not hold tasklist or siglock, we can race with fork/exit and copy the wrong results into cputimer->cputime. It is unneeded because if ->running == true we can just use the numbers in cputimer->cputime we already have. Change fastpath_timer_check() to copy cputimer->cputime into the local variable under cputimer->lock. We do not re-check ->running under cputimer->lock, run_posix_cpu_timers() does this check later. Note: we can add more optimizations on top of this change. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <20100611180446.GA13025@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* | sched: run_posix_cpu_timers: Don't check ->exit_state, use lock_task_sighand()Oleg Nesterov2010-06-181-6/+4
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | run_posix_cpu_timers() doesn't work if current has already passed exit_notify(). This was needed to prevent the races with do_wait(). Since ea6d290c ->signal is always valid and can't go away. We can remove the "tsk->exit_state == 0" in fastpath_timer_check() and convert run_posix_cpu_timers() to use lock_task_sighand(). Note: it makes sense to take group_leader's sighand instead, the sub-thread still uses CPU after release_task(). But we need more changes to do this. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <20100610231018.GA25942@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* | sched: thread_group_cputime: Simplify, document the "alive" checkOleg Nesterov2010-06-181-14/+7
|/ | | | | | | | | | | | | | | | | | | | | | | | | | thread_group_cputime() looks as if it is rcu-safe, but in fact this was wrong until ea6d290c which pins task->signal to task_struct. It checks ->sighand != NULL under rcu, but this can't help if ->signal can go away. Fortunately the caller either holds ->siglock, or it is fastpath_timer_check() which uses current and checks exit_state == 0. - Since ea6d290c commit tsk->signal is stable, we can read it first and avoid the initialization from INIT_CPUTIME. - Even if tsk->signal is always valid, we still have to check it is safe to use next_thread() under rcu_read_lock(). Currently the code checks ->sighand != NULL, change it to use pid_alive() which is commonly used to ensure the task wasn't unhashed before we take rcu_read_lock(). Add the comment to explain this check. - Change the main loop to use the while_each_thread() helper. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <20100610230956.GA25921@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* posix-cpu-timers: avoid "task->signal != NULL" checksOleg Nesterov2010-05-271-6/+6
| | | | | | | | | | | | | | | | | | | | | | | | | Preparation to make task->signal immutable, no functional changes. posix-cpu-timers.c checks task->signal != NULL to ensure this task is alive and didn't pass __exit_signal(). This is correct but we are going to change the lifetime rules for ->signal and never reset this pointer. Change the code to check ->sighand instead, it doesn't matter which pointer we check under tasklist, they both are cleared simultaneously. As Roland pointed out, some of these changes are not strictly needed and probably it makes sense to revert them later, when ->signal will be pinned to task_struct. But this patch tries to ensure the subsequent changes in fork/exit can't make any visible impact on posix cpu timers. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Cc: Fenghua Yu <fenghua.yu@intel.com> Acked-by: Roland McGrath <roland@redhat.com> Cc: Stanislaw Gruszka <sgruszka@redhat.com> Cc: Tony Luck <tony.luck@intel.com> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* posix-cpu-timers: Optimize run_posix_cpu_timers()Stanislaw Gruszka2010-05-101-51/+29
| | | | | | | | | | | | | | | | | | | | We can optimize and simplify things taking into account signal->cputimer is always running when we have configured any process wide cpu timer. In check_process_timers(), we don't have to check if new updated value of signal->cputime_expires is smaller, since we maintain new first expiration time ({prof,virt,sched}_expires) in code flow and all other writes to expiration cache are protected by sighand->siglock . Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@elte.hu> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com> Cc: Balbir Singh <balbir@in.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
* Merge branch 'linus' into timers/coreThomas Gleixner2010-05-101-3/+7
|\ | | | | | | | | | | Reason: Further posix_cpu_timer patches depend on mainline changes Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
| * Merge branch 'timers-fixes-for-linus' of ↵Linus Torvalds2010-03-261-3/+7
| |\ | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip * 'timers-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: time: Fix accumulation bug triggered by long delay. posix-cpu-timers: Reset expire cache when no timer is running timer stats: Fix del_timer_sync() and try_to_del_timer_sync() clockevents: Sanitize min_delta_ns adjustment and prevent overflows