The patch titled
Subject: freezer: do not send a fake signal to a PF_DUMPCORE thread
has been removed from the -mm tree. Its filename was
freezer-do-not-send-a-fake-signal-to-a-pf_dumpcore-thread.patch
This patch was dropped because an updated version will be merged
------------------------------------------------------
From: Oleg Nesterov <oleg@xxxxxxxxxx>
Subject: freezer: do not send a fake signal to a PF_DUMPCORE thread
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 <oleg@xxxxxxxxxx>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
Cc: Mandeep Singh Baines <msb@xxxxxxxxxxxx>
Cc: Neil Horman <nhorman@xxxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/freezer.c | 19 ++++++++++++-------
1 file changed, 12 insertions(+), 7 deletions(-)
diff -puN kernel/freezer.c~freezer-do-not-send-a-fake-signal-to-a-pf_dumpcore-thread kernel/freezer.c
--- a/kernel/freezer.c~freezer-do-not-send-a-fake-signal-to-a-pf_dumpcore-thread
+++ a/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 t
* @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);
_
Patches currently in -mm which might be from oleg@xxxxxxxxxx are
thinkpad-acpi-kill-hotkey_thread_mutex.patch
lockdep-introduce-lock_acquire_exclusive-shared-helper-macros.patch
lglock-update-lockdep-annotations-to-report-recursive-local-locks.patch
ptrace-add-ability-to-retrieve-signals-without-removing-from-a-queue-v4.patch
selftest-add-a-test-case-for-ptrace_peeksiginfo.patch
coredump-only-sigkill-should-interrupt-the-coredumping-task.patch
coredump-ensure-that-sigkill-always-kills-the-dumping-thread.patch
coredump-sanitize-the-setting-of-signal-group_exit_code.patch
coredump-make-wait_for_dump_helpers-freezable.patch
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