diff options
author | Oleg Nesterov <oleg@redhat.com> | 2009-04-02 16:57:58 -0700 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2009-04-02 19:04:57 -0700 |
commit | 90bc8d8b1a38f1ab131a2399a202e1889db95de8 (patch) | |
tree | 97001737dc3c1c7fd364ddd995bcbfc1c27b4c3a /kernel/exit.c | |
parent | 6d7b2f5f9e88902b19f91d0c8a7ef58a5455f1a2 (diff) | |
download | kernel_samsung_tuna-90bc8d8b1a38f1ab131a2399a202e1889db95de8.zip kernel_samsung_tuna-90bc8d8b1a38f1ab131a2399a202e1889db95de8.tar.gz kernel_samsung_tuna-90bc8d8b1a38f1ab131a2399a202e1889db95de8.tar.bz2 |
do_wait: fix waiting for the group stop with the dead leader
do_wait(WSTOPPED) assumes that p->state must be == TASK_STOPPED, this is
not true if the leader is already dead. Check SIGNAL_STOP_STOPPED instead
and use signal->group_exit_code.
Trivial test-case:
void *tfunc(void *arg)
{
pause();
return NULL;
}
int main(void)
{
pthread_t thr;
pthread_create(&thr, NULL, tfunc, NULL);
pthread_exit(NULL);
return 0;
}
It doesn't react to ^Z (and then to ^C or ^\). The task is stopped, but
bash can't see this.
The bug is very old, and it was reported multiple times. This patch was sent
more than a year ago (http://marc.info/?t=119713920000003) but it was ignored.
This change also fixes other oddities (but not all) in this area. For
example, before this patch:
$ sleep 100
^Z
[1]+ Stopped sleep 100
$ strace -p `pidof sleep`
Process 11442 attached - interrupt to quit
strace hangs in do_wait(), because ->exit_code was already consumed by
bash. After this patch, strace happily proceeds:
--- SIGTSTP (Stopped) @ 0 (0) ---
restart_syscall(<... resuming interrupted call ...>
To me, this looks much more "natural" and correct.
Another example. Let's suppose we have the main thread M and sub-thread
T, the process is stopped, and its parent did wait(WSTOPPED). Now we can
ptrace T but not M. This looks at least strange to me.
Imho, do_wait() should not confuse the per-thread ptrace stops with the
per-process job control stops.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Jan Kratochvil <jan.kratochvil@redhat.com>
Cc: Kaz Kylheku <kkylheku@gmail.com>
Cc: Michael Kerrisk <mtk.manpages@googlemail.com>
Cc: Roland McGrath <roland@redhat.com>
Cc: Ulrich Drepper <drepper@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/exit.c')
-rw-r--r-- | kernel/exit.c | 30 |
1 files changed, 18 insertions, 12 deletions
diff --git a/kernel/exit.c b/kernel/exit.c index 167e1e3..0c06b9e 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -1417,6 +1417,18 @@ static int wait_task_zombie(struct task_struct *p, int options, return retval; } +static int *task_stopped_code(struct task_struct *p, bool ptrace) +{ + if (ptrace) { + if (task_is_stopped_or_traced(p)) + return &p->exit_code; + } else { + if (p->signal->flags & SIGNAL_STOP_STOPPED) + return &p->signal->group_exit_code; + } + return NULL; +} + /* * Handle sys_wait4 work for one task in state TASK_STOPPED. We hold * read_lock(&tasklist_lock) on entry. If we return zero, we still hold @@ -1427,7 +1439,7 @@ static int wait_task_stopped(int ptrace, struct task_struct *p, int options, struct siginfo __user *infop, int __user *stat_addr, struct rusage __user *ru) { - int retval, exit_code, why; + int retval, exit_code, *p_code, why; uid_t uid = 0; /* unneeded, required by compiler */ pid_t pid; @@ -1437,22 +1449,16 @@ static int wait_task_stopped(int ptrace, struct task_struct *p, exit_code = 0; spin_lock_irq(&p->sighand->siglock); - if (unlikely(!task_is_stopped_or_traced(p))) - goto unlock_sig; - - if (!ptrace && p->signal->group_stop_count > 0) - /* - * A group stop is in progress and this is the group leader. - * We won't report until all threads have stopped. - */ + p_code = task_stopped_code(p, ptrace); + if (unlikely(!p_code)) goto unlock_sig; - exit_code = p->exit_code; + exit_code = *p_code; if (!exit_code) goto unlock_sig; if (!unlikely(options & WNOWAIT)) - p->exit_code = 0; + *p_code = 0; /* don't need the RCU readlock here as we're holding a spinlock */ uid = __task_cred(p)->uid; @@ -1608,7 +1614,7 @@ static int wait_consider_task(struct task_struct *parent, int ptrace, */ *notask_error = 0; - if (task_is_stopped_or_traced(p)) + if (task_stopped_code(p, ptrace)) return wait_task_stopped(ptrace, p, options, infop, stat_addr, ru); |