(apologies to all, re-send to fedora-kernel-list(a)redhat.com) (the patch targets 2.6.26 fedora kernels, don't know what should be in SUBJECT). See https://bugzilla.redhat.com/show_bug.cgi?id=469684 utrace_report_syscall_entry() must recalc_sigpending() unconditionally. While we slept in TASK_TRACED the new signals can be queued, but in that case TIF_SIGPENDING is not set. See the (correct) task_is_stopped_or_traced() check in wants_signal(). Signed-off-by: Oleg Nesterov <oleg(a)redhat.com&gt; --- linux-2.6.26.x86_64/kernel/utrace.c~UTRACE_SIGLOST 2008-10-09 17:47:14.000000000 +0200 +++ linux-2.6.26.x86_64/kernel/utrace.c 2008-11-30 23:15:33.000000000 +0100 @@ -1383,20 +1383,21 @@ bool utrace_report_syscall_entry(struct if (unlikely(report.result == UTRACE_SYSCALL_ABORT)) return true; - if (signal_pending(task)) { - /* - * Clear TIF_SIGPENDING if it no longer needs to be set. - * It may have been set as part of quiescence, and won't - * ever have been cleared by another thread. For other - * reports, we can just leave it set and will go through - * utrace_get_signal() to reset things. But here we are - * about to enter a syscall, which might bail out with an - * -ERESTART* error if it's set now. - */ - spin_lock_irq(&task->sighand->siglock); - recalc_sigpending(); - spin_unlock_irq(&task->sighand->siglock); - } + /* + * Clear TIF_SIGPENDING if it no longer needs to be set. + * It may have been set as part of quiescence, and won't + * ever have been cleared by another thread. For other + * reports, we can just leave it set and will go through + * utrace_get_signal() to reset things. But here we are + * about to enter a syscall, which might bail out with an + * -ERESTART* error if it's set now. + * + * Or, set TIF_SIGPENDING if the signal was queued while + * we were stopped in TASK_TRACED. + */ + spin_lock_irq(&task->sighand->siglock); + recalc_sigpending(); + spin_unlock_irq(&task->sighand->siglock); return false; }