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authorOleg Nesterov <oleg@tv-sign.ru>2006-01-08 01:03:13 -0800
committerLinus Torvalds <torvalds@g5.osdl.org>2006-01-08 20:13:55 -0800
commitbb6f6dbaa48c53525a7a4f9d4df719c3b0b582af (patch)
treed8214a72c61d49e3cb896e0390256f23e9f72eff
parent0811af28ce49fab963e3e6b8abcf8c460f971cd4 (diff)
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[PATCH] do_coredump() should reset group_stop_count earlier
__group_complete_signal() sets ->group_stop_count in sig_kernel_coredump() path and marks the target thread as ->group_exit_task. So any thread except group_exit_task will go to handle_group_stop()->finish_stop(). However, when group_exit_task actually starts do_coredump(), it sets SIGNAL_GROUP_EXIT, but does not reset ->group_stop_count while killing other threads. If we have not yet stopped threads in the same thread group, they all will spin in kernel mode until group_exit_task sends them SIGKILL, because ->group_stop_count > 0 means: recalc_sigpending_tsk() never clears TIF_SIGPENDING get_signal_to_deliver() goes to handle_group_stop() handle_group_stop() returns when SIGNAL_GROUP_EXIT set syscall_exit/resume_userspace notice TIF_SIGPENDING, call get_signal_to_deliver() again. So we are wasting cpu cycles, and if one of these threads is rt_task() this may be a serious problem. NOTE: do_coredump() holds ->mmap_sem, so not stopped threads can't escape coredumping after clearing ->group_stop_count. See also this thread: http://marc.theaimsgroup.com/?t=112739139900002 Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
-rw-r--r--fs/exec.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/fs/exec.c b/fs/exec.c
index 2075b674d85e..fd02ea4a81e9 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1462,6 +1462,7 @@ int do_coredump(long signr, int exit_code, struct pt_regs * regs)
if (!(current->signal->flags & SIGNAL_GROUP_EXIT)) {
current->signal->flags = SIGNAL_GROUP_EXIT;
current->signal->group_exit_code = exit_code;
+ current->signal->group_stop_count = 0;
retval = 0;
}
spin_unlock_irq(&current->sighand->siglock);
@@ -1477,7 +1478,6 @@ int do_coredump(long signr, int exit_code, struct pt_regs * regs)
* Clear any false indication of pending signals that might
* be seen by the filesystem code called to write the core file.
*/
- current->signal->group_stop_count = 0;
clear_thread_flag(TIF_SIGPENDING);
if (current->signal->rlim[RLIMIT_CORE].rlim_cur < binfmt->min_coredump)