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bcachefs: six locks: Guard against wakee exiting in __six_lock_wakeup()

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Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
This commit is contained in:
Kent Overstreet 2023-08-12 17:10:42 -04:00
parent 93ee2c4b21
commit f854ce4d0a
1 changed files with 8 additions and 1 deletions
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9
fs/bcachefs/six.c
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@ -8,6 +8,7 @@
#include <linux/sched.h>
#include <linux/sched/clock.h>
#include <linux/sched/rt.h>
#include <linux/sched/task.h>
#include <linux/slab.h>
#include "six.h"
@ -221,7 +222,12 @@ again:
if (ret <= 0)
goto unlock;
task = w->task;
/*
* Similar to percpu_rwsem_wake_function(), we need to guard
* against the wakee noticing w->lock_acquired, returning, and
* then exiting before we do the wakeup:
*/
task = get_task_struct(w->task);
__list_del(w->list.prev, w->list.next);
/*
* The release barrier here ensures the ordering of the
@ -232,6 +238,7 @@ again:
*/
smp_store_release(&w->lock_acquired, true);
wake_up_process(task);
put_task_struct(task);
}
six_clear_bitmask(lock, SIX_LOCK_WAITING_read << lock_type);