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authorTejun Heo <tj@kernel.org>2011-11-22 00:32:23 +0400
committerTejun Heo <tj@kernel.org>2011-11-22 00:32:23 +0400
commit8a32c441c1609f80e55df75422324a1151208f40 (patch)
tree73884b06cc2db3ea155af9a88815bb5105a4473e /include/linux/freezer.h
parenta0acae0e886d44bd5ce6d2f173c1ace0fcf0d9f6 (diff)
downloadlinux-8a32c441c1609f80e55df75422324a1151208f40.tar.xz
freezer: implement and use kthread_freezable_should_stop()
Writeback and thinkpad_acpi have been using thaw_process() to prevent deadlock between the freezer and kthread_stop(); unfortunately, this is inherently racy - nothing prevents freezing from happening between thaw_process() and kthread_stop(). This patch implements kthread_freezable_should_stop() which enters refrigerator if necessary but is guaranteed to return if kthread_stop() is invoked. Both thaw_process() users are converted to use the new function. Note that this deadlock condition exists for many of freezable kthreads. They need to be converted to use the new should_stop or freezable workqueue. Tested with synthetic test case. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Henrique de Moraes Holschuh <ibm-acpi@hmh.eng.br> Cc: Jens Axboe <axboe@kernel.dk> Cc: Oleg Nesterov <oleg@redhat.com>
Diffstat (limited to 'include/linux/freezer.h')
-rw-r--r--include/linux/freezer.h6
1 files changed, 3 insertions, 3 deletions
diff --git a/include/linux/freezer.h b/include/linux/freezer.h
index 7a9427e9fe47..d02b78448b0f 100644
--- a/include/linux/freezer.h
+++ b/include/linux/freezer.h
@@ -47,7 +47,7 @@ static inline bool should_send_signal(struct task_struct *p)
/* Takes and releases task alloc lock using task_lock() */
extern int thaw_process(struct task_struct *p);
-extern bool __refrigerator(void);
+extern bool __refrigerator(bool check_kthr_stop);
extern int freeze_processes(void);
extern int freeze_kernel_threads(void);
extern void thaw_processes(void);
@@ -57,7 +57,7 @@ static inline bool try_to_freeze(void)
might_sleep();
if (likely(!freezing(current)))
return false;
- return __refrigerator();
+ return __refrigerator(false);
}
extern bool freeze_task(struct task_struct *p, bool sig_only);
@@ -180,7 +180,7 @@ static inline void set_freeze_flag(struct task_struct *p) {}
static inline void clear_freeze_flag(struct task_struct *p) {}
static inline int thaw_process(struct task_struct *p) { return 1; }
-static inline bool __refrigerator(void) { return false; }
+static inline bool __refrigerator(bool check_kthr_stop) { return false; }
static inline int freeze_processes(void) { return -ENOSYS; }
static inline int freeze_kernel_threads(void) { return -ENOSYS; }
static inline void thaw_processes(void) {}