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Commit 5c7edcd7 authored by Roland McGrath's avatar Roland McGrath Committed by Linus Torvalds
Browse files

tracehook: fix exit_signal=0 case 



My commit 2b2a1ff6 introduced a regression
(sorry about that) for the odd case of exit_signal=0 (e.g. clone_flags=0).
This is not a normal use, but it's used by a case in the glibc test suite.

Dying with exit_signal=0 sends no signal, but it's supposed to wake up a
parent's blocked wait*() calls (unlike the delayed_group_leader case).
This fixes tracehook_notify_death() and its caller to distinguish a
"signal 0" wakeup from the delayed_group_leader case (with no wakeup).

Signed-off-by: default avatarRoland McGrath <roland@redhat.com>
Tested-by: default avatarSerge Hallyn <serue@us.ibm.com>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 1e24b15b

include/linux/tracehook.h

+13 −8
Original line number Diff line number Diff line
@@ -493,16 +493,21 @@ static inline int tracehook_notify_jctl(int notify, int why) 
 * @death_cookie:	value to pass to tracehook_report_death()

 * @group_dead:		nonzero if this was the last thread in the group to die

 *

 * Return the signal number to send our parent with do_notify_parent(), or

 * zero to send no signal and leave a zombie, or -1 to self-reap right now.

 * A return value >= 0 means call do_notify_parent() with that signal

 * number.  Negative return value can be %DEATH_REAP to self-reap right

 * now, or %DEATH_DELAYED_GROUP_LEADER to a zombie without notifying our

 * parent.  Note that a return value of 0 means a do_notify_parent() call

 * that sends no signal, but still wakes up a parent blocked in wait*().

 *

 * Called with write_lock_irq(&tasklist_lock) held.

 */

#define DEATH_REAP			-1

#define DEATH_DELAYED_GROUP_LEADER	-2

static inline int tracehook_notify_death(struct task_struct *task,

					 void **death_cookie, int group_dead)

{

	if (task->exit_signal == -1)

		return task->ptrace ? SIGCHLD : -1;

		return task->ptrace ? SIGCHLD : DEATH_REAP;



	/*

	 * If something other than our normal parent is ptracing us, then
@@ -512,21 +517,21 @@ static inline int tracehook_notify_death(struct task_struct *task, 
	if (thread_group_empty(task) && !ptrace_reparented(task))

		return task->exit_signal;



	return task->ptrace ? SIGCHLD : 0;

	return task->ptrace ? SIGCHLD : DEATH_DELAYED_GROUP_LEADER;

}



/**

 * tracehook_report_death - task is dead and ready to be reaped

 * @task:		@current task now exiting

 * @signal:		signal number sent to parent, or 0 or -1

 * @signal:		return value from tracheook_notify_death()

 * @death_cookie:	value passed back from tracehook_notify_death()

 * @group_dead:		nonzero if this was the last thread in the group to die

 *

 * Thread has just become a zombie or is about to self-reap.  If positive,

 * @signal is the signal number just sent to the parent (usually %SIGCHLD).

 * If @signal is -1, this thread will self-reap.  If @signal is 0, this is

 * a delayed_group_leader() zombie.  The @death_cookie was passed back by

 * tracehook_notify_death().

 * If @signal is %DEATH_REAP, this thread will self-reap.  If @signal is

 * %DEATH_DELAYED_GROUP_LEADER, this is a delayed_group_leader() zombie.

 * The @death_cookie was passed back by tracehook_notify_death().

 *

 * If normal reaping is not inhibited, @task->exit_state might be changing

 * in parallel.

kernel/exit.c

+3 −3
Original line number Diff line number Diff line
@@ -911,10 +911,10 @@ static void exit_notify(struct task_struct *tsk, int group_dead) 
		tsk->exit_signal = SIGCHLD;



	signal = tracehook_notify_death(tsk, &cookie, group_dead);

	if (signal > 0)

	if (signal >= 0)

		signal = do_notify_parent(tsk, signal);



	tsk->exit_state = signal < 0 ? EXIT_DEAD : EXIT_ZOMBIE;

	tsk->exit_state = signal == DEATH_REAP ? EXIT_DEAD : EXIT_ZOMBIE;



	/* mt-exec, de_thread() is waiting for us */

	if (thread_group_leader(tsk) &&
@@ -927,7 +927,7 @@ static void exit_notify(struct task_struct *tsk, int group_dead) 
	tracehook_report_death(tsk, signal, cookie, group_dead);



	/* If the process is dead, release it - nobody will wait for it */

	if (signal < 0)

	if (signal == DEATH_REAP)

		release_task(tsk);

}