Messages in this thread Patch in this message | | | Date | Mon, 31 Oct 2011 19:15:11 -0700 | From | Tejun Heo <> | Subject | [PATCH pm] freezer: fix wait_event_freezable/__thaw_task races |
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From: Oleg Nesterov <oleg@redhat.com>
wait_event_freezable() and friends stop the waiting if try_to_freeze() fails. This is not right, we can race with __thaw_task() and in this case
- wait_event_freezable() returns the wrong ERESTARTSYS
- wait_event_freezable_timeout() can return the positive value while condition == F
Change the code to always check __retval/condition before return.
Note: with or without this patch the timeout logic looks strange, probably we should recalc timeout if try_to_freeze() returns T.
tj: Updated to apply to wait_event_freezekillable() too.
Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Tejun Heo <tj@kernel.org> ---
So, this should be the last of lost patches. It's on top of
linus/master +[1] freezer: fix various bugs and simplify implementation, take#2 +[2] usb_storage: don't use set_freezable_with_signal()" + [3] +[3] freezer: kill unused set_freezable_with_signal()
and available in the following git branch.
git://git.kernel.org/pub/scm/linux/kernel/git/tj/misc.git pm-fix-wait_freezable
Thank you.
[1] http://thread.gmane.org/gmane.linux.kernel/1209247 [2] http://thread.gmane.org/gmane.linux.kernel/1209416 [3] http://thread.gmane.org/gmane.linux.kernel/1209416/focus=1209417
include/linux/freezer.h | 27 ++++++++++++++------------- 1 files changed, 14 insertions(+), 13 deletions(-)
diff --git a/include/linux/freezer.h b/include/linux/freezer.h index 5f32321..4a1d933 100644 --- a/include/linux/freezer.h +++ b/include/linux/freezer.h @@ -113,42 +113,43 @@ static inline int freezer_should_skip(struct task_struct *p) #define wait_event_freezekillable(wq, condition) \ ({ \ int __retval; \ - do { \ + for (;;) { \ __retval = wait_event_killable(wq, \ (condition) || freezing(current)); \ - if (__retval && !freezing(current)) \ + if (__retval || (condition)) \ break; \ - else if (!(condition)) \ - __retval = -ERESTARTSYS; \ - } while (try_to_freeze()); \ + try_to_freeze(); \ + } \ __retval; \ }) #define wait_event_freezable(wq, condition) \ ({ \ int __retval; \ - do { \ + for (;;) { \ __retval = wait_event_interruptible(wq, \ (condition) || freezing(current)); \ - if (__retval && !freezing(current)) \ + if (__retval || (condition)) \ break; \ - else if (!(condition)) \ - __retval = -ERESTARTSYS; \ - } while (try_to_freeze()); \ + try_to_freeze(); \ + } \ __retval; \ }) - #define wait_event_freezable_timeout(wq, condition, timeout) \ ({ \ long __retval = timeout; \ - do { \ + for (;;) { \ __retval = wait_event_interruptible_timeout(wq, \ (condition) || freezing(current), \ __retval); \ - } while (try_to_freeze()); \ + if (__retval <= 0 || (condition)) \ + break; \ + try_to_freeze(); \ + } \ __retval; \ }) + #else /* !CONFIG_FREEZER */ static inline bool frozen(struct task_struct *p) { return false; } static inline bool freezing(struct task_struct *p) { return false; } -- 1.7.3.1
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