The patch titled signals: do_tkill: don't use tasklist_lock has been removed from the -mm tree. Its filename was signals-do_tkill-dont-use-tasklist_lock.patch This patch was dropped because it was merged into mainline or a subsystem tree The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/ ------------------------------------------------------ Subject: signals: do_tkill: don't use tasklist_lock From: Oleg Nesterov <oleg@xxxxxxxxxx> Convert do_tkill() to use rcu_read_lock() + lock_task_sighand() to avoid taking tasklist lock. 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. Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx> Cc: Roland McGrath <roland@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- kernel/signal.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) diff -puN kernel/signal.c~signals-do_tkill-dont-use-tasklist_lock kernel/signal.c --- a/kernel/signal.c~signals-do_tkill-dont-use-tasklist_lock +++ a/kernel/signal.c @@ -2219,6 +2219,7 @@ static int do_tkill(int tgid, int pid, i int error; struct siginfo info; struct task_struct *p; + unsigned long flags; error = -ESRCH; info.si_signo = sig; @@ -2227,21 +2228,24 @@ static int do_tkill(int tgid, int pid, i info.si_pid = task_tgid_vnr(current); info.si_uid = current->uid; - read_lock(&tasklist_lock); + rcu_read_lock(); p = find_task_by_vpid(pid); if (p && (tgid <= 0 || task_tgid_vnr(p) == tgid)) { error = check_kill_permission(sig, &info, p); /* * 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 && p->sighand) { - spin_lock_irq(&p->sighand->siglock); + if (!error && sig && lock_task_sighand(p, &flags)) { error = specific_send_sig_info(sig, &info, p); - spin_unlock_irq(&p->sighand->siglock); + unlock_task_sighand(p, &flags); } } - read_unlock(&tasklist_lock); + rcu_read_unlock(); return error; } _ Patches currently in -mm which might be from oleg@xxxxxxxxxx are origin.patch posix-timers-bug-10460-discard-the-pending-signal-when-the-timer-is-destroyed.patch workqueue-remove-redundant-function-invocation.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