Messages in this thread Patch in this message | | | Date | Fri, 16 Nov 2007 20:24:13 +0300 | From | Oleg Nesterov <> | Subject | [PATCH 2/3] wait_task_stopped: tidy up the noreap case |
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wait_task_stopped(WNOWAIT) unlocks tasklist_lock and re-checks ->exit_code and ->exit_state. This is not needed: both were valid before we dropped the lock, and without tasklist_lock both are not stable anyway.
Read the exit_code under tasklist and report the cached value without re-check. In fact this fixes the race with the dying child, we can report a completely false exit_code if ->exit_state is not visible yet.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
--- 24/kernel/exit.c~2_NOREAP 2007-11-16 18:13:54.000000000 +0300 +++ 24/kernel/exit.c 2007-11-16 18:18:24.000000000 +0300 @@ -1356,10 +1356,10 @@ static int wait_task_stopped(struct task int noreap, struct siginfo __user *infop, int __user *stat_addr, struct rusage __user *ru) { - int retval, exit_code; + int retval, exit_code = p->exit_code; pid_t pid; - if (!p->exit_code) + if (!exit_code) return 0; if (delayed_group_leader && !(p->ptrace & PT_PTRACED) && p->signal->group_stop_count > 0) @@ -1384,9 +1384,6 @@ static int wait_task_stopped(struct task uid_t uid = p->uid; int why = (p->ptrace & PT_PTRACED) ? CLD_TRAPPED : CLD_STOPPED; - exit_code = p->exit_code; - if (unlikely(!exit_code) || unlikely(p->exit_state)) - goto bail_ref; return wait_noreap_copyout(p, pid, uid, why, (exit_code << 8) | 0x7f, infop, ru); @@ -1417,7 +1414,6 @@ static int wait_task_stopped(struct task * resumed, or it resumed and then died. */ write_unlock_irq(&tasklist_lock); -bail_ref: put_task_struct(p); /* * We are returning to the wait loop without having successfully - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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