Commit 6f35c4ab authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Rafael J. Wysocki

PM / Freezer: Reimplement wait_event_freezekillable using freezer_do_not_count/freezer_count

Commit 27920651 "PM / Freezer: Make fake_signal_wake_up() wake
TASK_KILLABLE tasks too" updated fake_signal_wake_up() used by freezer
to wake up KILLABLE tasks.  Sending unsolicited wakeups to tasks in
killable sleep is dangerous as there are code paths which depend on
tasks not waking up spuriously from KILLABLE sleep.

For example. sys_read() or page can sleep in TASK_KILLABLE assuming
that wait/down/whatever _killable can only fail if we can not return
to the usermode.  TASK_TRACED is another obvious example.

The offending commit was to resolve freezer hang during system PM
operations caused by KILLABLE sleeps in network filesystems.
wait_event_freezekillable(), which depends on the spurious KILLABLE
wakeup, was added by f06ac72e "cifs, freezer: add
wait_event_freezekillable and have cifs use it" to be used to
implement killable & freezable sleeps in network filesystems.

To prepare for reverting of 27920651, this patch reimplements
wait_event_freezekillable() using freezer_do_not_count/freezer_count()
so that it doesn't depend on the spurious KILLABLE wakeup.  This isn't
very nice but should do for now.

[tj: Refreshed patch to apply to linus/master and updated commit
    description on Rafael's request.]
Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Signed-off-by: default avatarRafael J. Wysocki <rjw@sisk.pl>
parent b2c0a863
...@@ -143,14 +143,9 @@ static inline void set_freezable_with_signal(void) ...@@ -143,14 +143,9 @@ static inline void set_freezable_with_signal(void)
#define wait_event_freezekillable(wq, condition) \ #define wait_event_freezekillable(wq, condition) \
({ \ ({ \
int __retval; \ int __retval; \
do { \ freezer_do_not_count(); \
__retval = wait_event_killable(wq, \ __retval = wait_event_killable(wq, (condition)); \
(condition) || freezing(current)); \ freezer_count(); \
if (__retval && !freezing(current)) \
break; \
else if (!(condition)) \
__retval = -ERESTARTSYS; \
} while (try_to_freeze()); \
__retval; \ __retval; \
}) })
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment