The patch titled signals-do_tkill-dont-use-tasklist_lock-comment has been added to the -mm tree. Its filename is signals-do_tkill-dont-use-tasklist_lock-comment.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://www.zip.com.au/~akpm/linux/patches/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: signals-do_tkill-dont-use-tasklist_lock-comment From: Oleg Nesterov <oleg@xxxxxxxxxx> On 03/07, Christoph Hellwig wrote: > > On Fri, Mar 07, 2008 at 12:58:13PM +0300, Oleg Nesterov wrote: > > Note that we don't return an error if lock_task_sighand() fails, we pretend the > > task dies after receiving the signal. Otherwise, we should fight with the nasty > > races with mt-exec without having any advantage. > > This should be mentioned in a comment in the code. Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx> Cc: Roland McGrath <roland@xxxxxxxxxx> Cc: Christoph Hellwig <hch@xxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- kernel/signal.c | 4 ++++ 1 file changed, 4 insertions(+) diff -puN kernel/signal.c~signals-do_tkill-dont-use-tasklist_lock-comment kernel/signal.c --- a/kernel/signal.c~signals-do_tkill-dont-use-tasklist_lock-comment +++ a/kernel/signal.c @@ -2222,6 +2222,10 @@ static int do_tkill(int tgid, int pid, i /* * The null signal is a permissions and process existence * probe. No signal is actually delivered. + * + * If lock_task_sighand() fails we pretend the task dies + * after receiving the signal. The window is tiny, and the + * signal is private anyway. */ if (!error && sig && lock_task_sighand(p, &flags)) { error = specific_send_sig_info(sig, &info, p); _ Patches currently in -mm which might be from oleg@xxxxxxxxxx are git-hrt.patch kthread-call-wake_up_process-without-the-lock-being-held.patch mmap_region-cleanup-the-final-vma_merge-related-code.patch remove-unused-variable-from-send_signal.patch turn-legacy_queue-macro-into-static-inline-function.patch consolidate-checking-for-ignored-legacy-signals.patch consolidate-checking-for-ignored-legacy-signals-simplify.patch signals-do_signal_stop-use-signal_group_exit.patch signals-do_group_exit-use-signal_group_exit-more-consistently.patch lock_task_sighand-add-rcu-lock-unlock.patch k_getrusage-dont-take-rcu_read_lock.patch do_task_stat-dont-take-rcu_read_lock.patch signals-consolidate-checks-for-whether-or-not-to-ignore-a-signal.patch signals-clean-dequeue_signal-from-excess-checks-and-assignments.patch signals-consolidate-send_sigqueue-and-send_group_sigqueue.patch signals-cleanup-security_task_kill-usage-implementation.patch signals-re-assign-cld_continued-notification-from-the-sender-to-reciever.patch kill_pid_info-dont-take-now-unneeded-tasklist_lock.patch handle_stop_signal-unify-partial-full-stop-handling.patch handle_stop_signal-use-the-cached-p-signal-value.patch get_signal_to_deliver-use-the-cached-signal-sighand-values.patch signals-send_sigqueue-dont-take-rcu-lock.patch signals-send_sigqueue-dont-forget-about-handle_stop_signal.patch signals-__group_complete_signal-cache-the-value-of-p-signal.patch signals-send_group_sigqueue-dont-take-tasklist_lock.patch signals-move-handle_stop_signal-into-send_signal.patch signals-do_tkill-dont-use-tasklist_lock.patch signals-do_tkill-dont-use-tasklist_lock-comment.patch signals-send_sig_info-dont-take-tasklist_lock.patch ptrace-introduce-task_detached-helper.patch reparent_thread-use-same_thread_group.patch document-de_thread-with-exit_notify-connection.patch ptrace-introduce-ptrace_reparented-helper.patch ptrace-__ptrace_unlink-use-the-ptrace_reparented-helper.patch workqueues-shrink-cpu_populated_map-when-cpu-dies.patch workqueues-shrink-cpu_populated_map-when-cpu-dies-fix.patch cleanup_workqueue_thread-remove-the-unneeded-cpu-parameter.patch simplify-cpu_hotplug_begin-put_online_cpus.patch redo-locking-of-tty-pgrp.patch resume-tty-on-susp-and-fix-crnl-order-in-n_tty-line-discipline.patch tty_io-fix-remaining-pid-struct-locking.patch tty_io-fix-remaining-pid-struct-locking-small-cleanup.patch procfs-task-exe-symlink.patch procfs-task-exe-symlink-fix.patch procfs-task-exe-symlink-fix-2.patch free_pidmap-turn-it-into-free_pidmapstruct-upid.patch put_pid-make-sure-we-dont-free-the-live-pid.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