A coredumping thread can't be frozen anyway but the fake signal sent
by freeze_task() can confuse dump_write/wait_for_dump_helpers/etc
and interrupt the coredump.
We are going to make the do_coredump() paths freezable but the fake
TIF_SIGPENDING doesn't help, it only makes sense when we assume that
the target can return to user-mode and call get_signal_to_deliver().
Change freeze_task() to check PF_DUMPCORE along with PF_KTHREAD. We
need to recheck PF_DUMPCORE under ->siglock to avoid the race with
zap_threads() which can set this flag right before we take the lock.
Signed-off-by: Oleg Nesterov <o...@redhat.com>
---
kernel/freezer.c | 19 ++++++++++++-------
1 files changed, 12 insertions(+), 7 deletions(-)
diff --git a/kernel/freezer.c b/kernel/freezer.c
index c38893b..595afab 100644
--- a/kernel/freezer.c
+++ b/kernel/freezer.c
@@ -85,14 +85,21 @@ bool __refrigerator(bool check_kthr_stop)
}
EXPORT_SYMBOL(__refrigerator);
-static void fake_signal_wake_up(struct task_struct *p)
+static bool fake_signal_wake_up(struct task_struct *p)
{
unsigned long flags;
+ bool ret = false;
+
+ if (p->flags & (PF_KTHREAD | PF_DUMPCORE))
+ return ret;
if (lock_task_sighand(p, &flags)) {
- signal_wake_up(p, 0);
+ ret = !(p->flags & PF_DUMPCORE);
+ if (ret)
+ signal_wake_up(p, 0);
unlock_task_sighand(p, &flags);
}
+ return ret;
}
/**
@@ -100,8 +107,8 @@ static void fake_signal_wake_up(struct task_struct *p)
* @p: task to send the request to
*
* If @p is freezing, the freeze request is sent either by sending a fake
- * signal (if it's not a kernel thread) or waking it up (if it's a kernel
- * thread).
+ * signal (if it's not a kernel thread or a coredumping thread) or waking
+ * it up otherwise.
*
* RETURNS:
* %false, if @p is not freezing or already frozen; %true, otherwise
@@ -116,9 +123,7 @@ bool freeze_task(struct task_struct *p)
return false;
}
- if (!(p->flags & PF_KTHREAD))
- fake_signal_wake_up(p);
- else
+ if (!fake_signal_wake_up(p))
wake_up_state(p, TASK_INTERRUPTIBLE);
spin_unlock_irqrestore(&freezer_lock, flags);
--
1.5.5.1
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