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tracehook: fix exit_signal=0 case

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My commit 2b2a1ff64a 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: Roland McGrath <roland@redhat.com>
Tested-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Roland McGrath 2008-07-31 02:04:09 -07:00 committed by Linus Torvalds
parent 1e24b15b26
commit 5c7edcd7ee
2 changed files with 16 additions and 11 deletions
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21
include/linux/tracehook.h
View file

@ -493,16 +493,21 @@ static inline int tracehook_notify_jctl(int notify, int why)
* @death_cookie: value to pass to tracehook_report_death() * @death_cookie: value to pass to tracehook_report_death()
* @group_dead: nonzero if this was the last thread in the group to die * @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 * A return value >= 0 means call do_notify_parent() with that signal
* zero to send no signal and leave a zombie, or -1 to self-reap right now. * 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. * 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, static inline int tracehook_notify_death(struct task_struct *task,
void **death_cookie, int group_dead) void **death_cookie, int group_dead)
{ {
if (task->exit_signal == -1) 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 * 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)) if (thread_group_empty(task) && !ptrace_reparented(task))
return task->exit_signal; 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 * tracehook_report_death - task is dead and ready to be reaped
* @task: @current task now exiting * @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() * @death_cookie: value passed back from tracehook_notify_death()
* @group_dead: nonzero if this was the last thread in the group to die * @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, * 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). * @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 * If @signal is %DEATH_REAP, this thread will self-reap. If @signal is
* a delayed_group_leader() zombie. The @death_cookie was passed back by * %DEATH_DELAYED_GROUP_LEADER, this is a delayed_group_leader() zombie.
* tracehook_notify_death(). * The @death_cookie was passed back by tracehook_notify_death().
* *
* If normal reaping is not inhibited, @task->exit_state might be changing * If normal reaping is not inhibited, @task->exit_state might be changing
* in parallel. * in parallel.

6
kernel/exit.c
View file

@ -911,10 +911,10 @@ static void exit_notify(struct task_struct *tsk, int group_dead)
tsk->exit_signal = SIGCHLD; tsk->exit_signal = SIGCHLD;
signal = tracehook_notify_death(tsk, &cookie, group_dead); signal = tracehook_notify_death(tsk, &cookie, group_dead);
if (signal > 0) if (signal >= 0)
signal = do_notify_parent(tsk, signal); 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 */ /* mt-exec, de_thread() is waiting for us */
if (thread_group_leader(tsk) && 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); tracehook_report_death(tsk, signal, cookie, group_dead);
/* If the process is dead, release it - nobody will wait for it */ /* If the process is dead, release it - nobody will wait for it */
if (signal < 0) if (signal == DEATH_REAP)
release_task(tsk); release_task(tsk);
} }