The patch titled exit: avoid sig->count in de_thread/__exit_signal synchronization has been added to the -mm tree. Its filename is exit-avoid-sig-count-in-de_thread-__exit_signal-synchronization.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** See http://userweb.kernel.org/~akpm/stuff/added-to-mm.txt to find out what to do about this The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/ ------------------------------------------------------ Subject: exit: avoid sig->count in de_thread/__exit_signal synchronization From: Oleg Nesterov <oleg@xxxxxxxxxx> de_thread() and __exit_signal() use signal_struct->count/notify_count for synchronization. We can simplify the code and use ->notify_count only. Instead of comparing these two counters, we can change de_thread() to set ->notify_count = nr_of_sub_threads, then change __exit_signal() to dec-and-test this counter and notify group_exit_task. Note that __exit_signal() checks "notify_count > 0" just for symmetry with exit_notify(), we could just check it is != 0. Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx> Acked-by: Roland McGrath <roland@xxxxxxxxxx> Cc: Veaceslav Falico <vfalico@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- fs/exec.c | 11 +++++------ kernel/exit.c | 2 +- 2 files changed, 6 insertions(+), 7 deletions(-) diff -puN fs/exec.c~exit-avoid-sig-count-in-de_thread-__exit_signal-synchronization fs/exec.c --- a/fs/exec.c~exit-avoid-sig-count-in-de_thread-__exit_signal-synchronization +++ a/fs/exec.c @@ -763,7 +763,6 @@ static int de_thread(struct task_struct struct signal_struct *sig = tsk->signal; struct sighand_struct *oldsighand = tsk->sighand; spinlock_t *lock = &oldsighand->siglock; - int count; if (thread_group_empty(tsk)) goto no_thread_group; @@ -780,13 +779,13 @@ static int de_thread(struct task_struct spin_unlock_irq(lock); return -EAGAIN; } + sig->group_exit_task = tsk; - zap_other_threads(tsk); + sig->notify_count = zap_other_threads(tsk); + if (!thread_group_leader(tsk)) + sig->notify_count--; - /* Account for the thread group leader hanging around: */ - count = thread_group_leader(tsk) ? 1 : 2; - sig->notify_count = count; - while (atomic_read(&sig->count) > count) { + while (sig->notify_count) { __set_current_state(TASK_UNINTERRUPTIBLE); spin_unlock_irq(lock); schedule(); diff -puN kernel/exit.c~exit-avoid-sig-count-in-de_thread-__exit_signal-synchronization kernel/exit.c --- a/kernel/exit.c~exit-avoid-sig-count-in-de_thread-__exit_signal-synchronization +++ a/kernel/exit.c @@ -98,7 +98,7 @@ static void __exit_signal(struct task_st * If there is any task waiting for the group exit * then notify it: */ - if (sig->group_exit_task && atomic_read(&sig->count) == sig->notify_count) + if (sig->notify_count > 0 && !--sig->notify_count) wake_up_process(sig->group_exit_task); if (tsk == sig->curr_target) _ Patches currently in -mm which might be from oleg@xxxxxxxxxx are origin.patch linux-next.patch posix-cpu-timers-reset-expire-cache-when-no-timer-is-running.patch cpu-timers-simplify-rlimit_cpu-handling.patch cpu-timers-cleanup-arm_timer.patch cpu-timers-return-correct-previous-timer-reload-value.patch cpu-timers-change-sigev_none-timer-implementation.patch cpu-timers-assure-to-not-iterate-over-all-threads-in-fastpath_timer_check.patch cpu-timers-optimize-run_posix_cpu_timers.patch proc-cleanup-remove-unused-assignments.patch kmod-add-init-function-to-usermodehelper.patch exec-replace-call_usermodehelper_pipe-with-use-of-umh-init-function-and-resolve-limit.patch umh-creds-convert-call_usermodehelper_keys-to-use-subprocess_info-init.patch umh-creds-kill-subprocess_info-cred-logic.patch call_usermodehelper-no-need-to-unblock-signals.patch wait_for_helper-sigchld-from-user-space-can-lead-to-use-after-free.patch call_usermodehelper-simplify-fix-umh_no_wait-case.patch call_usermodehelper-umh_wait_exec-ignores-kernel_thread-failure.patch coredump-factor-out-the-not-ispipe-file-checks.patch coredump-cleanup-ispipe-code.patch coredump-factor-out-put_cred-calls.patch coredump-shift-down_writemmap_sem-into-coredump_wait.patch exit-exit_notify-can-trust-signal-notify_count-0.patch exit-change-zap_other_threads-to-count-sub-threads.patch exit-avoid-sig-count-in-de_thread-__exit_signal-synchronization.patch exit-avoid-sig-count-in-__exit_signal-to-detect-the-group-dead-case.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html