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author | Tejun Heo <tj@kernel.org> | 2011-06-02 11:14:00 +0200 |
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committer | Oleg Nesterov <oleg@redhat.com> | 2011-06-04 18:17:11 +0200 |
commit | 7dd3db54e77d21eb95e145f19ba53f68250d0e73 (patch) | |
tree | 628e44b22e6fbf2828cf2c533c41b3d24f3e3ec9 /kernel | |
parent | 6dfca32984237a8a011b5bf367e53341a265b2a4 (diff) | |
download | linux-stable-7dd3db54e77d21eb95e145f19ba53f68250d0e73.tar.gz linux-stable-7dd3db54e77d21eb95e145f19ba53f68250d0e73.tar.bz2 linux-stable-7dd3db54e77d21eb95e145f19ba53f68250d0e73.zip |
job control: introduce task_set_jobctl_pending()
task->jobctl currently hosts JOBCTL_STOP_PENDING and will host TRAP
pending bits too. Setting pending conditions on a dying task may make
the task unkillable. Currently, each setting site is responsible for
checking for the condition but with to-be-added job control traps this
becomes too fragile.
This patch adds task_set_jobctl_pending() which should be used when
setting task->jobctl bits to schedule a stop or trap. The function
performs the followings to ease setting pending bits.
* Sanity checks.
* If fatal signal is pending or PF_EXITING is set, no bit is set.
* STOP_SIGMASK is automatically cleared if new value is being set.
do_signal_stop() and ptrace_attach() are updated to use
task_set_jobctl_pending() instead of setting STOP_PENDING explicitly.
The surrounding structures around setting are changed to fit
task_set_jobctl_pending() better but there should be no userland
visible behavior difference.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Diffstat (limited to 'kernel')
-rw-r--r-- | kernel/ptrace.c | 6 | ||||
-rw-r--r-- | kernel/signal.c | 46 |
2 files changed, 43 insertions, 9 deletions
diff --git a/kernel/ptrace.c b/kernel/ptrace.c index eb191116edf7..0c37d999c8b8 100644 --- a/kernel/ptrace.c +++ b/kernel/ptrace.c @@ -256,10 +256,10 @@ static int ptrace_attach(struct task_struct *task) * The following task_is_stopped() test is safe as both transitions * in and out of STOPPED are protected by siglock. */ - if (task_is_stopped(task)) { - task->jobctl |= JOBCTL_STOP_PENDING | JOBCTL_TRAPPING; + if (task_is_stopped(task) && + task_set_jobctl_pending(task, + JOBCTL_STOP_PENDING | JOBCTL_TRAPPING)) signal_wake_up(task, 1); - } spin_unlock(&task->sighand->siglock); diff --git a/kernel/signal.c b/kernel/signal.c index 637a171b65b6..9ab91c516c3f 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -224,6 +224,39 @@ static inline void print_dropped_signal(int sig) } /** + * task_set_jobctl_pending - set jobctl pending bits + * @task: target task + * @mask: pending bits to set + * + * Clear @mask from @task->jobctl. @mask must be subset of + * %JOBCTL_PENDING_MASK | %JOBCTL_STOP_CONSUME | %JOBCTL_STOP_SIGMASK | + * %JOBCTL_TRAPPING. If stop signo is being set, the existing signo is + * cleared. If @task is already being killed or exiting, this function + * becomes noop. + * + * CONTEXT: + * Must be called with @task->sighand->siglock held. + * + * RETURNS: + * %true if @mask is set, %false if made noop because @task was dying. + */ +bool task_set_jobctl_pending(struct task_struct *task, unsigned int mask) +{ + BUG_ON(mask & ~(JOBCTL_PENDING_MASK | JOBCTL_STOP_CONSUME | + JOBCTL_STOP_SIGMASK | JOBCTL_TRAPPING)); + BUG_ON((mask & JOBCTL_TRAPPING) && !(mask & JOBCTL_PENDING_MASK)); + + if (unlikely(fatal_signal_pending(task) || (task->flags & PF_EXITING))) + return false; + + if (mask & JOBCTL_STOP_SIGMASK) + task->jobctl &= ~JOBCTL_STOP_SIGMASK; + + task->jobctl |= mask; + return true; +} + +/** * task_clear_jobctl_trapping - clear jobctl trapping bit * @task: target task * @@ -1902,19 +1935,20 @@ static int do_signal_stop(int signr) else WARN_ON_ONCE(!task_ptrace(current)); - current->jobctl &= ~JOBCTL_STOP_SIGMASK; - current->jobctl |= signr | gstop; - sig->group_stop_count = 1; + sig->group_stop_count = 0; + + if (task_set_jobctl_pending(current, signr | gstop)) + sig->group_stop_count++; + for (t = next_thread(current); t != current; t = next_thread(t)) { - t->jobctl &= ~JOBCTL_STOP_SIGMASK; /* * Setting state to TASK_STOPPED for a group * stop is always done with the siglock held, * so this check has no races. */ - if (!(t->flags & PF_EXITING) && !task_is_stopped(t)) { - t->jobctl |= signr | gstop; + if (!task_is_stopped(t) && + task_set_jobctl_pending(t, signr | gstop)) { sig->group_stop_count++; signal_wake_up(t, 0); } |