projects / thirdparty / kernel / stable-queue.git / blame
| Commit | Line | Data |
|---|---|---|
| 867615e6 GKH |
1 | From 6d69cb87f05eef3b02370b2f7bae608ad2301a00 Mon Sep 17 00:00:00 2001 |
| 2 | From: Oleg Nesterov <oleg@redhat.com> | |
| 3 | Date: Thu, 2 Apr 2009 16:58:12 -0700 | |
| 4 | Subject: ptrace: simplify ptrace_exit()->ignoring_children() path | |
| 5 | ||
| 6 | From: Oleg Nesterov <oleg@redhat.com> | |
| 7 | ||
| 8 | commit 6d69cb87f05eef3b02370b2f7bae608ad2301a00 upstream. | |
| 9 | ||
| 10 | ignoring_children() takes parent->sighand->siglock and checks | |
| 11 | k_sigaction[SIGCHLD] atomically. But this buys nothing, we can't get the | |
| 12 | "really" wrong result even if we race with sigaction(SIGCHLD). If we read | |
| 13 | the "stale" sa_handler/sa_flags we can pretend it was changed right after | |
| 14 | the check. | |
| 15 | ||
| 16 | Remove spin_lock(->siglock), and kill "int ign" which caches the result of | |
| 17 | ignoring_children() which becomes rather trivial. | |
| 18 | ||
| 19 | Perhaps it makes sense to export this helper, do_notify_parent() can use | |
| 20 | it too. | |
| 21 | ||
| 22 | Signed-off-by: Oleg Nesterov <oleg@redhat.com> | |
| 23 | Cc: Jerome Marchand <jmarchan@redhat.com> | |
| 24 | Cc: Roland McGrath <roland@redhat.com> | |
| 25 | Cc: Denys Vlasenko <dvlasenk@redhat.com> | |
| 26 | Signed-off-by: Andrew Morton <akpm@linux-foundation.org> | |
| 27 | Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> | |
| 28 | Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de> | |
| 29 | ||
| 30 | --- | |
| 31 | kernel/exit.c | 25 ++++++++----------------- | |
| 32 | 1 file changed, 8 insertions(+), 17 deletions(-) | |
| 33 | ||
| 34 | --- a/kernel/exit.c | |
| 35 | +++ b/kernel/exit.c | |
| 36 | @@ -703,19 +703,15 @@ static void exit_mm(struct task_struct * | |
| 37 | } | |
| 38 | ||
| 39 | /* | |
| 40 | - * Return nonzero if @parent's children should reap themselves. | |
| 41 | - * | |
| 42 | - * Called with write_lock_irq(&tasklist_lock) held. | |
| 43 | + * Called with irqs disabled, returns true if childs should reap themselves. | |
| 44 | */ | |
| 45 | -static int ignoring_children(struct task_struct *parent) | |
| 46 | +static int ignoring_children(struct sighand_struct *sigh) | |
| 47 | { | |
| 48 | int ret; | |
| 49 | - struct sighand_struct *psig = parent->sighand; | |
| 50 | - unsigned long flags; | |
| 51 | - spin_lock_irqsave(&psig->siglock, flags); | |
| 52 | - ret = (psig->action[SIGCHLD-1].sa.sa_handler == SIG_IGN || | |
| 53 | - (psig->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDWAIT)); | |
| 54 | - spin_unlock_irqrestore(&psig->siglock, flags); | |
| 55 | + spin_lock(&sigh->siglock); | |
| 56 | + ret = (sigh->action[SIGCHLD-1].sa.sa_handler == SIG_IGN) || | |
| 57 | + (sigh->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDWAIT); | |
| 58 | + spin_unlock(&sigh->siglock); | |
| 59 | return ret; | |
| 60 | } | |
| 61 | ||
| 62 | @@ -728,7 +724,6 @@ static int ignoring_children(struct task | |
| 63 | static void ptrace_exit(struct task_struct *parent, struct list_head *dead) | |
| 64 | { | |
| 65 | struct task_struct *p, *n; | |
| 66 | - int ign = -1; | |
| 67 | ||
| 68 | list_for_each_entry_safe(p, n, &parent->ptraced, ptrace_entry) { | |
| 69 | __ptrace_unlink(p); | |
| 70 | @@ -750,12 +745,8 @@ static void ptrace_exit(struct task_stru | |
| 71 | if (!task_detached(p) && thread_group_empty(p)) { | |
| 72 | if (!same_thread_group(p->real_parent, parent)) | |
| 73 | do_notify_parent(p, p->exit_signal); | |
| 74 | - else { | |
| 75 | - if (ign < 0) | |
| 76 | - ign = ignoring_children(parent); | |
| 77 | - if (ign) | |
| 78 | - p->exit_signal = -1; | |
| 79 | - } | |
| 80 | + else if (ignoring_children(parent->sighand)) | |
| 81 | + p->exit_signal = -1; | |
| 82 | } | |
| 83 | ||
| 84 | if (task_detached(p)) { |