The patch titled
do_signal_stop: do not call tracehook_notify_jctl() in TASK_STOPPED state
has been added to the -mm tree. Its filename is
signals-tracehook_notify_jctl-change-do_signal_stop-do-not-call-tracehook_notify_jctl-in-task_stopped-state.patch
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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: do_signal_stop: do not call tracehook_notify_jctl() in TASK_STOPPED state
From: Oleg Nesterov <oleg@xxxxxxxxxx>
do_signal_stop() can call tracehook_notify_jctl() before decrementing
->group_stop_count and setting TASK_STOPPED/SIGNAL_STOP_STOPPED.
This way the tracing hooks can drop and reacquire the siglock freely and
do any blocking hooks without potential SIGCONT races.
With this patch TASK_STOPPED/SIGNAL_STOP_STOPPED is set only when we know
for sure we are going to schedule() after unlock(siglock).
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Roland McGrath <roland@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/signal.c | 40 ++++++++++++++++++----------------------
1 file changed, 18 insertions(+), 22 deletions(-)
diff -puN kernel/signal.c~signals-tracehook_notify_jctl-change-do_signal_stop-do-not-call-tracehook_notify_jctl-in-task_stopped-state kernel/signal.c
--- a/kernel/signal.c~signals-tracehook_notify_jctl-change-do_signal_stop-do-not-call-tracehook_notify_jctl-in-task_stopped-state
+++ a/kernel/signal.c
@@ -1673,16 +1673,9 @@ void ptrace_notify(int exit_code)
static int do_signal_stop(int signr)
{
struct signal_struct *sig = current->signal;
- int stop_count;
int notify;
- if (sig->group_stop_count > 0) {
- /*
- * There is a group stop in progress. We don't need to
- * start another one.
- */
- stop_count = --sig->group_stop_count;
- } else {
+ if (!sig->group_stop_count) {
struct task_struct *t;
if (!likely(sig->flags & SIGNAL_STOP_DEQUEUED) ||
@@ -1694,7 +1687,7 @@ static int do_signal_stop(int signr)
*/
sig->group_exit_code = signr;
- stop_count = 0;
+ sig->group_stop_count = 1;
for (t = next_thread(current); t != current; t = next_thread(t))
/*
* Setting state to TASK_STOPPED for a group
@@ -1703,25 +1696,28 @@ static int do_signal_stop(int signr)
*/
if (!(t->flags & PF_EXITING) &&
!task_is_stopped_or_traced(t)) {
- stop_count++;
+ sig->group_stop_count++;
signal_wake_up(t, 0);
}
- sig->group_stop_count = stop_count;
}
-
- if (stop_count == 0)
- sig->flags = SIGNAL_STOP_STOPPED;
- current->exit_code = sig->group_exit_code;
- __set_current_state(TASK_STOPPED);
-
/*
* If there are no other threads in the group, or if there is
- * a group stop in progress and we are the last to stop,
- * report to the parent. When ptraced, every thread reports itself.
+ * a group stop in progress and we are the last to stop, report
+ * to the parent. When ptraced, every thread reports itself.
*/
- notify = tracehook_notify_jctl(stop_count == 0 ? CLD_STOPPED : 0,
- CLD_STOPPED);
-
+ notify = sig->group_stop_count == 1 ? CLD_STOPPED : 0;
+ notify = tracehook_notify_jctl(notify, CLD_STOPPED);
+ /*
+ * tracehook_notify_jctl() can drop and reacquire siglock, so
+ * we keep ->group_stop_count != 0 before the call. If SIGCONT
+ * or SIGKILL comes in between ->group_stop_count == 0.
+ */
+ if (sig->group_stop_count) {
+ if (!--sig->group_stop_count)
+ sig->flags = SIGNAL_STOP_STOPPED;
+ current->exit_code = sig->group_exit_code;
+ __set_current_state(TASK_STOPPED);
+ }
spin_unlock_irq(¤t->sighand->siglock);
if (notify) {
_
Patches currently in -mm which might be from oleg@xxxxxxxxxx are
origin.patch
linux-next.patch
getrusage-fill-ru_maxrss-value.patch
getrusage-fill-ru_maxrss-value-update.patch
proc_flush_task-flush-proc-tid-task-pid-when-a-sub-thread-exits.patch
ptrace-__ptrace_detach-do-__wake_up_parent-if-we-reap-the-tracee.patch
do_wait-wakeup-optimization-shift-security_task_wait-from-eligible_child-to-wait_consider_task.patch
do_wait-wakeup-optimization-change-__wake_up_parent-to-use-filtered-wakeup.patch
do_wait-wakeup-optimization-change-__wake_up_parent-to-use-filtered-wakeup-selinux_bprm_committed_creds-use-__wake_up_parent.patch
do_wait-wakeup-optimization-child_wait_callback-check-__wnothread-case.patch
do_wait-optimization-do-not-place-sub-threads-on-task_struct-children-list.patch
wait_consider_task-kill-parent-argument.patch
do_wait-fix-sys_waitid-specific-behaviour.patch
wait_noreap_copyout-check-for-wo_info-=-null.patch
signals-tracehook_notify_jctl-change.patch
signals-tracehook_notify_jctl-change-do_signal_stop-do-not-call-tracehook_notify_jctl-in-task_stopped-state.patch
utrace-core.patch
exec-fix-set_binfmt-vs-sys_delete_module-race.patch
fork-disable-clone_parent-for-init.patch
pidns-deny-clone_parentclone_newpid-combination.patch
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