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* [PATCH] Remove __devinit and __cpuinit from notifier_call definitionsChandra Seetharaman2006-04-261-1/+1
| | | | | | | | | | | | | Few of the notifier_chain_register() callers use __init in the definition of notifier_call. It is incorrect as the function definition should be available after the initializations (they do not unregister them during initializations). This patch fixes all such usages to _not_ have the notifier_call __init section. Signed-off-by: Chandra Seetharaman <sekharan@us.ibm.com> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] Remove __devinitdata from notifier block definitionsChandra Seetharaman2006-04-261-1/+1
| | | | | | | | | | | | | | | | Few of the notifier_chain_register() callers use __devinitdata in the definition of notifier_block data structure. It is incorrect as the data structure should be available after the initializations (they do not unregister them during initializations). This was leading to an oops when notifier_chain_register() call is invoked for those callback chains after initialization. This patch fixes all such usages to _not_ have the notifier_block data structure in the init data section. Signed-off-by: Chandra Seetharaman <sekharan@us.ibm.com> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] timer initialisation fixAndrew Morton2006-04-111-10/+19
| | | | | | | | | | | | | | | | | | We need the boot CPU's tvec_bases[] entry to be initialised super-early in boot, for early_serial_setup(). That runs within setup_arch(), before even per-cpu areas are initialised. The patch changes tvec_bases to use compile-time initialisation, and adds a separate array `tvec_base_done' to keep track of which CPU has had its tvec_bases[] entry initialised (because we can no longer use the zeroness of that tvec_bases[] entry to determine whether it has been initialised). Thanks to Eugene Surovegin <ebs@ebshome.net> for diagnosing this. Cc: Eugene Surovegin <ebs@ebshome.net> Cc: Jan Beulich <jbeulich@novell.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] x86_64: Fix drift with HPET timer enabledJordan Hargrave2006-04-091-1/+1
| | | | | | | | | | | | | | | | | | | | If the HPET timer is enabled, the clock can drift by ~3 seconds a day. This is due to the HPET timer not being initialized with the correct setting (still using PIT count). If HZ changes, this drift can become even more pronounced. HPET patch initializes tick_nsec with correct tick_nsec settings for HPET timer. Vojtech comments: "It's not entirely correct (it assumes the HPET ticks totally exactly), but it's significantly better than assuming the PIT error there." Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* BUG_ON() Conversion in kernel/signal.cEric Sesterhenn2006-04-021-2/+1
| | | | | | | | this changes if() BUG(); constructs to BUG_ON() which is cleaner, contains unlikely() and can better optimized away. Signed-off-by: Eric Sesterhenn <snakebyte@gmx.de> Signed-off-by: Adrian Bunk <bunk@stusta.de>
* [PATCH] sched: reduce overhead of calc_loadJack Steiner2006-03-311-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | Currently, count_active_tasks() calls both nr_running() & nr_interruptible(). Each of these functions does a "for_each_cpu" & reads values from the runqueue of each cpu. Although this is not a lot of instructions, each runqueue may be located on different node. Depending on the architecture, a unique TLB entry may be required to access each runqueue. Since there may be more runqueues than cpu TLB entries, a scan of all runqueues can trash the TLB. Each memory reference incurs a TLB miss & refill. In addition, the runqueue cacheline that contains nr_running & nr_uninterruptible may be evicted from the cache between the two passes. This causes unnecessary cache misses. Combining nr_running() & nr_interruptible() into a single function substantially reduces the TLB & cache misses on large systems. This should have no measureable effect on smaller systems. On a 128p IA64 system running a memory stress workload, the new function reduced the overhead of calc_load() from 605 usec/call to 324 usec/call. Signed-off-by: Jack Steiner <steiner@sgi.com> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] __mod_timer: simplify ->base changingOleg Nesterov2006-03-311-8/+6
| | | | | | | | | | Since base and new_base are of the same type now, we can save one 'if' branch and simplify the code a bit. Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] kill __init_timer_base in favor of boot_tvec_basesOleg Nesterov2006-03-311-49/+35
| | | | | | | | | | | | | Commit a4a6198b80cf82eb8160603c98da218d1bd5e104: [PATCH] tvec_bases too large for per-cpu data introduced "struct tvec_t_base_s boot_tvec_bases" which is visible at compile time. This means we can kill __init_timer_base and move timer_base_s's content into tvec_t_base_s. Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] remove pps supportRoman Zippel2006-03-251-11/+2
| | | | | | | | | | | | | | This removes the support for pps. It's completely unused within the kernel and is basically in the way for further cleanups. It should be easier to readd proper support for it after the rest has been converted to NTP4 (where the pps mechanisms are quite different from NTP3 anyway). Signed-off-by: Roman Zippel <zippel@linux-m68k.org> Cc: Adrian Bunk <bunk@stusta.de> Cc: john stultz <johnstul@us.ibm.com> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] sys_alarm() unsigned signed conversion fixupThomas Gleixner2006-03-251-13/+1
| | | | | | | | | | | | | | | | | | | | | | | | | alarm() calls the kernel with an unsigend int timeout in seconds. The value is stored in the tv_sec field of a struct timeval to setup the itimer. The tv_sec field of struct timeval is of type long, which causes the tv_sec value to be negative on 32 bit machines if seconds > INT_MAX. Before the hrtimer merge (pre 2.6.16) such a negative value was converted to the maximum jiffies timeout by the timeval_to_jiffies conversion. It's not clear whether this was intended or just happened to be done by the timeval_to_jiffies code. hrtimers expect a timeval in canonical form and treat a negative timeout as already expired. This breaks the legitimate usage of alarm() with a timeout value > INT_MAX seconds. For 32 bit machines it is therefor necessary to limit the internal seconds value to avoid API breakage. Instead of doing this in all implementations of sys_alarm the duplicated sys_alarm code is moved into a common function in itimer.c Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] timer-irq-driven soft-watchdog, cleanupsIngo Molnar2006-03-241-1/+1
| | | | | | | | | | | | | | | Make the softlockup detector purely timer-interrupt driven, removing softirq-context (timer) dependencies. This means that if the softlockup watchdog triggers, it has truly observed a longer than 10 seconds scheduling delay of a SCHED_FIFO prio 99 task. (the patch also turns off the softlockup detector during the initial bootup phase and does small style fixes) Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] tvec_bases too large for per-cpu dataJan Beulich2006-03-241-11/+34
| | | | | | | | | | | | | | | | With internal Xen-enabled kernels we see the kernel's static per-cpu data area exceed the limit of 32k on x86-64, and even native x86-64 kernels get fairly close to that limit. I generally question whether it is reasonable to have data structures several kb in size allocated as per-cpu data when the space there is rather limited. The biggest arch-independent consumer is tvec_bases (over 4k on 32-bit archs, over 8k on 64-bit ones), which now gets converted to use dynamically allocated memory instead. Signed-off-by: Jan Beulich <jbeulich@novell.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] time_interpolator: add __read_mostlyChristoph Lameter2006-03-171-2/+2
| | | | | | | | | | The pointer to the current time interpolator and the current list of time interpolators are typically only changed during bootup. Adding __read_mostly takes them away from possibly hot cachelines. Signed-off-by: Christoph Lameter <clameter@sgi.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] time: add barrier after updating jiffies_64Atsushi Nemoto2006-03-061-0/+2
| | | | | | | | | | | Add a compiler barrier so that we don't read jiffies before updating jiffies_64. Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp> Cc: Ralf Baechle <ralf@linux-mips.org> Cc: Paul Mackerras <paulus@samba.org> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] fix next_timer_interrupt() for hrtimerTony Lindgren2006-03-061-0/+16
| | | | | | | | | | | | | | | | | | | | | Also from Thomas Gleixner <tglx@linutronix.de> Function next_timer_interrupt() got broken with a recent patch 6ba1b91213e81aa92b5cf7539f7d2a94ff54947c as sys_nanosleep() was moved to hrtimer. This broke things as next_timer_interrupt() did not check hrtimer tree for next event. Function next_timer_interrupt() is needed with dyntick (CONFIG_NO_IDLE_HZ, VST) implementations, as the system can be in idle when next hrtimer event was supposed to happen. At least ARM and S390 currently use next_timer_interrupt(). Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: Russell King <rmk@arm.linux.org.uk> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] time_interpolator: Use readq_relaxed() instead of readq().Christoph Lameter2006-03-021-2/+2
| | | | | | | | | | | | | | | | On some platforms readq performs additional work to make sure I/O is done in a coherent way. This is not needed for time retrieval as done by the time interpolator. So we can use readq_relaxed instead which will improve performance. It affects sparc64 and ia64 only. Apparently it makes a significant difference on ia64. Signed-off-by: Christoph Lameter <clameter@sgi.com> Cc: john stultz <johnstul@us.ibm.com> Cc: "David S. Miller" <davem@davemloft.net> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] Provide an interface for getting the current tick lengthPaul Mackerras2006-02-171-5/+34
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This provides an interface for arch code to find out how many nanoseconds are going to be added on to xtime by the next call to do_timer. The value returned is a fixed-point number in 52.12 format in nanoseconds. The reason for this format is that it gives the full precision that the timekeeping code is using internally. The motivation for this is to fix a problem that has arisen on 32-bit powerpc in that the value returned by do_gettimeofday drifts apart from xtime if NTP is being used. PowerPC is now using a lockless do_gettimeofday based on reading the timebase register and performing some simple arithmetic. (This method of getting the time is also exported to userspace via the VDSO.) However, the factor and offset it uses were calculated based on the nominal tick length and weren't being adjusted when NTP varied the tick length. Note that 64-bit powerpc has had the lockless do_gettimeofday for a long time now. It also had an extremely hairy routine that got called from the 32-bit compat routine for adjtimex, which adjusted the factor and offset according to what it thought the timekeeping code was going to do. Not only was this only called if a 32-bit task did adjtimex (i.e. not if a 64-bit task did adjtimex), it was also duplicating computations from kernel/timer.c and it wasn't clear that it was (still) correct. The simple solution is to ask the timekeeping code how long the current jiffy will be on each timer interrupt, after calling do_timer. If this jiffy will be a different length from the last one, we then need to compute new values for the factor and offset used in the lockless do_gettimeofday. In this way we can keep xtime and do_gettimeofday in sync, even when NTP is varying the tick length. Note that when adjtimex varies the tick length, it almost always introduces the variation from the next tick on. The only case I could see where adjtimex would vary the length of the current tick is when an old-style adjtime adjustment is being cancelled. (It's not clear to me why the adjustment has to be cancelled immediately rather than from the next tick on.) Thus I don't see any real need for a hook in adjtimex; the rare case of an old-style adjustment being cancelled can be fixed up at the next tick. Signed-off-by: Paul Mackerras <paulus@samba.org> Acked-by: john stultz <johnstul@us.ibm.com> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] timer.c NULL noise removalAl Viro2006-02-071-1/+1
| | | | Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* [PATCH] hrtimer: switch sys_nanosleep to hrtimerThomas Gleixner2006-01-101-56/+0
| | | | | | | | | convert sys_nanosleep() to use hrtimer_nanosleep() Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] hrtimer: hrtimer core codeThomas Gleixner2006-01-101-0/+1
| | | | | | | | | | hrtimer subsystem core. It is initialized at bootup and expired by the timer interrupt, but is otherwise not utilized by any other subsystem yet. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] kernel/: small cleanupsAdrian Bunk2006-01-081-0/+1
| | | | | | | | | | | | This patch contains the following cleanups: - make needlessly global functions static - every file should include the headers containing the prototypes for it's global functions Signed-off-by: Adrian Bunk <bunk@stusta.de> Acked-by: "Paul E. McKenney" <paulmck@us.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] jiffies_64 cleanupThomas Gleixner2005-10-301-0/+4
| | | | | | | | | Define jiffies_64 in kernel/timer.c rather than having 24 duplicated defines in each architecture. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] remove timer debug fieldAndrew Morton2005-10-301-35/+0
| | | | | | | | | | | | | | | | Remove timer_list.magic and associated debugging code. I originally added this when a spinlock was added to timer_list - this meant that an all-zeroes timer became illegal and init_timer() was required. That spinlock isn't even there any more, although timer.base must now be initialised. I'll keep this debugging code in -mm. Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] ntp whitespace cleanupAndrew Morton2005-10-301-126/+126
| | | | | | | Fix bizarre 4-space coding style in the NTP code. Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] NTP shift_right cleanupjohn stultz2005-10-301-42/+11
| | | | | | | | | | | | | | | | | | | | | | | | Create a macro shift_right() that avoids the numerous ugly conditionals in the NTP code that look like: if(a < 0) b = -(-a >> shift); else b = a >> shift; Replacing it with: b = shift_right(a, shift); This should have zero effect on the logic, however it should probably have a bit of testing just to be sure. Also replace open-coded min/max with the macros. Signed-off-by : John Stultz <johnstul@us.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] introduce setup_timer() helperOleg Nesterov2005-10-301-6/+2
| | | | | | | | | | | Every user of init_timer() also needs to initialize ->function and ->data fields. This patch adds a simple setup_timer() helper for that. The schedule_timeout() is patched as an example of usage. Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] TIMERS: add missing compensation for HZ == 250YOSHIFUJI Hideaki2005-10-291-0/+9
| | | | | | | | | | Add missing compensation for (HZ == 250) != (1 << SHIFT_HZ) in second_overflow(). Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org> Cc: "David S. Miller" <davem@davemloft.net> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] schedule_timeout_[un]interruptible() speedupAndrew Morton2005-09-131-3/+6
| | | | | | | These functions don't need schedule_timeout()'s barrier. Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] kernel: fix-up schedule_timeout() usageNishanth Aravamudan2005-09-101-12/+6
| | | | | | | | | Use schedule_timeout_{,un}interruptible() instead of set_current_state()/schedule_timeout() to reduce kernel size. Signed-off-by: Nishanth Aravamudan <nacc@us.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] add schedule_timeout_{,un}interruptible() interfacesNishanth Aravamudan2005-09-101-0/+14
| | | | | | | | | | Add schedule_timeout_{,un}interruptible() interfaces so that schedule_timeout() callers don't have to worry about forgetting to add the set_current_state() call beforehand. Signed-off-by: Nishanth Aravamudan <nacc@us.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] optimize writer path in time_interpolator_get_counter()Alex Williamson2005-09-071-4/+13
| | | | | | | | | | | | | | | | Christoph Lameter <clameter@engr.sgi.com> When using a time interpolator that is susceptible to jitter there's potentially contention over a cmpxchg used to prevent time from going backwards. This is unnecessary when the caller holds the xtime write seqlock as all readers will be blocked from returning until the write is complete. We can therefore allow writers to insert a new value and exit rather than fight with CPUs who only hold a reader lock. Signed-off-by: Alex Williamson <alex.williamson@hp.com> Signed-off-by: Christoph Lameter <clameter@sgi.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] detect soft lockupsIngo Molnar2005-09-071-0/+1
| | | | | | | | | | | | | | | | | | | This patch adds a new kernel debug feature: CONFIG_DETECT_SOFTLOCKUP. When enabled then per-CPU watchdog threads are started, which try to run once per second. If they get delayed for more than 10 seconds then a callback from the timer interrupt detects this condition and prints out a warning message and a stack dump (once per lockup incident). The feature is otherwise non-intrusive, it doesnt try to unlock the box in any way, it only gets the debug info out, automatically, and on all CPUs affected by the lockup. Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Nishanth Aravamudan <nacc@us.ibm.com> Signed-Off-By: Matthias Urlichs <smurf@smurf.noris.de> Signed-off-by: Richard Purdie <rpurdie@rpsys.net> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] preempt race in getppidDavid Meybohm2005-08-231-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | With CONFIG_PREEMPT && !CONFIG_SMP, it's possible for sys_getppid to return a bogus value if the parent's task_struct gets reallocated after current->group_leader->real_parent is read: asmlinkage long sys_getppid(void) { int pid; struct task_struct *me = current; struct task_struct *parent; parent = me->group_leader->real_parent; RACE HERE => for (;;) { pid = parent->tgid; #ifdef CONFIG_SMP { struct task_struct *old = parent; /* * Make sure we read the pid before re-reading the * parent pointer: */ smp_rmb(); parent = me->group_leader->real_parent; if (old != parent) continue; } #endif break; } return pid; } If the process gets preempted at the indicated point, the parent process can go ahead and call exit() and then get wait()'d on to reap its task_struct. When the preempted process gets resumed, it will not do any further checks of the parent pointer on !CONFIG_SMP: it will read the bad pid and return. So, the same algorithm used when SMP is enabled should be used when preempt is enabled, which will recheck ->real_parent in this case. Signed-off-by: David Meybohm <dmeybohmlkml@bellsouth.net> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] kernel/timer: fix msleep_interruptible() commentDomen Puncer2005-06-251-1/+1
| | | | | | | | | | The comment for msleep_interruptible() is wrong, as it will ignore wait-queue events, but will wake up early for signals. Signed-off-by: Nishanth Aravamudan <nacc@us.ibm.com> Signed-off-by: Domen Puncer <domen@coderock.org> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] preempt_count is int - remove cast and don't assign to unsigned typeJesper Juhl2005-06-231-2/+6
| | | | | | | | | | | | | | | | | | | | | | In kernel/sched.c the return value from preempt_count() is cast to an int. That made sense when preempt_count was defined as different types on is not needed and should go away. The patch removes the cast. In kernel/timer.c the return value from preempt_count() is assigned to a variable of type u32 and then that unsigned value is later compared to preempt_count(). Since preempt_count() returns an int, an int is what should be used to store its return value. Storing the result in an unsigned 32bit integer made a tiny bit of sense back when preempt_count was different types on different archs, but no more - let's not play signed vs unsigned comparison games when we don't have to. The patch modifies the code to use an int to hold the value. While I was around that bit of code I also made two changes to a nearby (related) printk() - I modified it to specify the loglevel explicitly and also broke the line into a few pieces to avoid it being longer than 80 chars and clarified the text a bit. Signed-off-by: Jesper Juhl <juhl-lkml@dif.dk> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] timers: introduce try_to_del_timer_sync()Oleg Nesterov2005-06-231-20/+33
| | | | | | | | | | | | | | | | | | This patch splits del_timer_sync() into 2 functions. The new one, try_to_del_timer_sync(), returns -1 when it hits executing timer. It can be used in interrupt context, or when the caller hold locks which can prevent completion of the timer's handler. NOTE. Currently it can't be used in interrupt context in UP case, because ->running_timer is used only with CONFIG_SMP. Should the need arise, it is possible to kill #ifdef CONFIG_SMP in set_running_timer(), it is cheap. Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] timers fixes/improvementsOleg Nesterov2005-06-231-171/+157
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This patch tries to solve following problems: 1. del_timer_sync() is racy. The timer can be fired again after del_timer_sync have checked all cpus and before it will recheck timer_pending(). 2. It has scalability problems. All cpus are scanned to determine if the timer is running on that cpu. With this patch del_timer_sync is O(1) and no slower than plain del_timer(pending_timer), unless it has to actually wait for completion of the currently running timer. The only restriction is that the recurring timer should not use add_timer_on(). 3. The timers are not serialized wrt to itself. If CPU_0 does mod_timer(jiffies+1) while the timer is currently running on CPU 1, it is quite possible that local interrupt on CPU_0 will start that timer before it finished on CPU_1. 4. The timers locking is suboptimal. __mod_timer() takes 3 locks at once and still requires wmb() in del_timer/run_timers. The new implementation takes 2 locks sequentially and does not need memory barriers. Currently ->base != NULL means that the timer is pending. In that case ->base.lock is used to lock the timer. __mod_timer also takes timer->lock because ->base can be == NULL. This patch uses timer->entry.next != NULL as indication that the timer is pending. So it does __list_del(), entry->next = NULL instead of list_del() when the timer is deleted. The ->base field is used for hashed locking only, it is initialized in init_timer() which sets ->base = per_cpu(tvec_bases). When the tvec_bases.lock is locked, it means that all timers which are tied to this base via timer->base are locked, and the base itself is locked too. So __run_timers/migrate_timers can safely modify all timers which could be found on ->tvX lists (pending timers). When the timer's base is locked, and the timer removed from ->entry list (which means that _run_timers/migrate_timers can't see this timer), it is possible to set timer->base = NULL and drop the lock: the timer remains locked. This patch adds lock_timer_base() helper, which waits for ->base != NULL, locks the ->base, and checks it is still the same. __mod_timer() schedules the timer on the local CPU and changes it's base. However, it does not lock both old and new bases at once. It locks the timer via lock_timer_base(), deletes the timer, sets ->base = NULL, and unlocks old base. Then __mod_timer() locks new_base, sets ->base = new_base, and adds this timer. This simplifies the code, because AB-BA deadlock is not possible. __mod_timer() also ensures that the timer's base is not changed while the timer's handler is running on the old base. __run_timers(), del_timer() do not change ->base anymore, they only clear pending flag. So del_timer_sync() can test timer->base->running_timer == timer to detect whether it is running or not. We don't need timer_list->lock anymore, this patch kills it. We also don't need barriers. del_timer() and __run_timers() used smp_wmb() before clearing timer's pending flag. It was needed because __mod_timer() did not lock old_base if the timer is not pending, so __mod_timer()->list_add() could race with del_timer()->list_del(). With this patch these functions are serialized through base->lock. One problem. TIMER_INITIALIZER can't use per_cpu(tvec_bases). So this patch adds global struct timer_base_s { spinlock_t lock; struct timer_list *running_timer; } __init_timer_base; which is used by TIMER_INITIALIZER. The corresponding fields in tvec_t_base_s struct are replaced by struct timer_base_s t_base. It is indeed ugly. But this can't have scalability problems. The global __init_timer_base.lock is used only when __mod_timer() is called for the first time AND the timer was compile time initialized. After that the timer migrates to the local CPU. Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Renaud Lienhart <renaud.lienhart@free.fr> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] use smp_mb/wmb/rmb where possibleakpm@osdl.org2005-05-011-1/+1
| | | | | | | | | Replace a number of memory barriers with smp_ variants. This means we won't take the unnecessary hit on UP machines. Signed-off-by: Anton Blanchard <anton@samba.org> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* Linux-2.6.12-rc2v2.6.12-rc2Linus Torvalds2005-04-161-0/+1611
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
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