diff options
| author | Tejun Heo <tj@kernel.org> | 2011-11-21 12:32:23 -0800 |
|---|---|---|
| committer | Tejun Heo <tj@kernel.org> | 2011-11-21 12:32:23 -0800 |
| commit | 8a32c441c1609f80e55df75422324a1151208f40 (patch) | |
| tree | 73884b06cc2db3ea155af9a88815bb5105a4473e /kernel | |
| parent | a0acae0e886d44bd5ce6d2f173c1ace0fcf0d9f6 (diff) | |
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 'kernel')
| -rw-r--r-- | kernel/freezer.c | 6 | ||||
| -rw-r--r-- | kernel/kthread.c | 25 |
2 files changed, 29 insertions, 2 deletions
diff --git a/kernel/freezer.c b/kernel/freezer.c index 732f14f5944f..b83c30e9483a 100644 --- a/kernel/freezer.c +++ b/kernel/freezer.c @@ -9,6 +9,7 @@ #include <linux/export.h> #include <linux/syscalls.h> #include <linux/freezer.h> +#include <linux/kthread.h> /* * freezing is complete, mark current process as frozen @@ -23,7 +24,7 @@ static inline void frozen_process(void) } /* Refrigerator is place where frozen processes are stored :-). */ -bool __refrigerator(void) +bool __refrigerator(bool check_kthr_stop) { /* Hmm, should we be allowed to suspend when there are realtime processes around? */ @@ -50,7 +51,8 @@ bool __refrigerator(void) for (;;) { set_current_state(TASK_UNINTERRUPTIBLE); - if (!frozen(current)) + if (!frozen(current) || + (check_kthr_stop && kthread_should_stop())) break; was_frozen = true; schedule(); diff --git a/kernel/kthread.c b/kernel/kthread.c index b6d216a92639..1c36deaae2f1 100644 --- a/kernel/kthread.c +++ b/kernel/kthread.c @@ -59,6 +59,31 @@ int kthread_should_stop(void) EXPORT_SYMBOL(kthread_should_stop); /** + * kthread_freezable_should_stop - should this freezable kthread return now? + * @was_frozen: optional out parameter, indicates whether %current was frozen + * + * kthread_should_stop() for freezable kthreads, which will enter + * refrigerator if necessary. This function is safe from kthread_stop() / + * freezer deadlock and freezable kthreads should use this function instead + * of calling try_to_freeze() directly. + */ +bool kthread_freezable_should_stop(bool *was_frozen) +{ + bool frozen = false; + + might_sleep(); + + if (unlikely(freezing(current))) + frozen = __refrigerator(true); + + if (was_frozen) + *was_frozen = frozen; + + return kthread_should_stop(); +} +EXPORT_SYMBOL_GPL(kthread_freezable_should_stop); + +/** * kthread_data - return data value specified on kthread creation * @task: kthread task in question * |