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author | Roland McGrath <roland@redhat.com> | 2008-04-08 23:12:30 -0700 |
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committer | Roland McGrath <roland@redhat.com> | 2008-07-16 18:02:34 -0700 |
commit | 666f164f4fbfa78bd00fb4b74788b42a39842c64 (patch) | |
tree | 27c6a77edbce3da0860b5bd05cf3a7a842140c2c /kernel/exit.c | |
parent | 14dd0b81414a58caf0296dbeace016bb0a5d11ab (diff) | |
download | kernel_samsung_smdk4412-666f164f4fbfa78bd00fb4b74788b42a39842c64.zip kernel_samsung_smdk4412-666f164f4fbfa78bd00fb4b74788b42a39842c64.tar.gz kernel_samsung_smdk4412-666f164f4fbfa78bd00fb4b74788b42a39842c64.tar.bz2 |
fix dangling zombie when new parent ignores children
This fixes an arcane bug that we think was a regression introduced
by commit b2b2cbc4b2a2f389442549399a993a8306420baf. When a parent
ignores SIGCHLD (or uses SA_NOCLDWAIT), its children would self-reap
but they don't if it's using ptrace on them. When the parent thread
later exits and ceases to ptrace a child but leaves other live
threads in the parent's thread group, any zombie children are left
dangling. The fix makes them self-reap then, as they would have
done earlier if ptrace had not been in use.
Signed-off-by: Roland McGrath <roland@redhat.com>
Diffstat (limited to 'kernel/exit.c')
-rw-r--r-- | kernel/exit.c | 26 |
1 files changed, 26 insertions, 0 deletions
diff --git a/kernel/exit.c b/kernel/exit.c index a2af6ca..93d2711 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -703,6 +703,23 @@ static void exit_mm(struct task_struct * tsk) } /* + * Return nonzero if @parent's children should reap themselves. + * + * Called with write_lock_irq(&tasklist_lock) held. + */ +static int ignoring_children(struct task_struct *parent) +{ + int ret; + struct sighand_struct *psig = parent->sighand; + unsigned long flags; + spin_lock_irqsave(&psig->siglock, flags); + ret = (psig->action[SIGCHLD-1].sa.sa_handler == SIG_IGN || + (psig->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDWAIT)); + spin_unlock_irqrestore(&psig->siglock, flags); + return ret; +} + +/* * Detach all tasks we were using ptrace on. * Any that need to be release_task'd are put on the @dead list. * @@ -711,6 +728,7 @@ static void exit_mm(struct task_struct * tsk) static void ptrace_exit(struct task_struct *parent, struct list_head *dead) { struct task_struct *p, *n; + int ign = -1; list_for_each_entry_safe(p, n, &parent->ptraced, ptrace_entry) { __ptrace_unlink(p); @@ -726,10 +744,18 @@ static void ptrace_exit(struct task_struct *parent, struct list_head *dead) * release_task() here because we already hold tasklist_lock. * * If it's our own child, there is no notification to do. + * But if our normal children self-reap, then this child + * was prevented by ptrace and we must reap it now. */ if (!task_detached(p) && thread_group_empty(p)) { if (!same_thread_group(p->real_parent, parent)) do_notify_parent(p, p->exit_signal); + else { + if (ign < 0) + ign = ignoring_children(parent); + if (ign) + p->exit_signal = -1; + } } if (task_detached(p)) { |