From 6b44f519017b219a12b37173c7eef8dfce2c0100 Mon Sep 17 00:00:00 2001 From: Scot Doyle Date: Sun, 24 Aug 2014 17:12:27 +0000 Subject: sched/wait: Document timeout corner case The timeout may elapse without 0 being returned, such as when waiting on an unused queue. Document this possibility. Signed-off-by: Scot Doyle Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Link: http://lkml.kernel.org/r/alpine.LNX.2.11.1408241710070.6462@localhost.localdomain Signed-off-by: Ingo Molnar --- include/linux/wait.h | 16 ++++++++++------ 1 file changed, 10 insertions(+), 6 deletions(-) (limited to 'include/linux/wait.h') diff --git a/include/linux/wait.h b/include/linux/wait.h index 6fb1ba5f9b2f..034f6fc7c65f 100644 --- a/include/linux/wait.h +++ b/include/linux/wait.h @@ -280,9 +280,11 @@ do { \ * wake_up() has to be called after changing any variable that could * change the result of the wait condition. * - * The function returns 0 if the @timeout elapsed, or the remaining - * jiffies (at least 1) if the @condition evaluated to %true before - * the @timeout elapsed. + * Returns: + * 0 if the @condition evaluated to %false after the @timeout elapsed, + * 1 if the @condition evaluated to %true after the @timeout elapsed, + * or the remaining jiffies (at least 1) if the @condition evaluated + * to %true before the @timeout elapsed. */ #define wait_event_timeout(wq, condition, timeout) \ ({ \ @@ -363,9 +365,11 @@ do { \ * change the result of the wait condition. * * Returns: - * 0 if the @timeout elapsed, -%ERESTARTSYS if it was interrupted by - * a signal, or the remaining jiffies (at least 1) if the @condition - * evaluated to %true before the @timeout elapsed. + * 0 if the @condition evaluated to %false after the @timeout elapsed, + * 1 if the @condition evaluated to %true after the @timeout elapsed, + * the remaining jiffies (at least 1) if the @condition evaluated + * to %true before the @timeout elapsed, or -%ERESTARTSYS if it was + * interrupted by a signal. */ #define wait_event_interruptible_timeout(wq, condition, timeout) \ ({ \ -- cgit v1.2.1 From cbbce82209490df8b68da9aec0d642451fe0a668 Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Thu, 25 Sep 2014 13:55:19 +1000 Subject: SCHED: add some "wait..on_bit...timeout()" interfaces. In commit c1221321b7c25b53204447cff9949a6d5a7ddddc sched: Allow wait_on_bit_action() functions to support a timeout I suggested that a "wait_on_bit_timeout()" interface would not meet my need. This isn't true - I was just over-engineering. Including a 'private' field in wait_bit_key instead of a focused "timeout" field was just premature generalization. If some other use is ever found, it can be generalized or added later. So this patch renames "private" to "timeout" with a meaning "stop waiting when "jiffies" reaches or passes "timeout", and adds two of the many possible wait..bit..timeout() interfaces: wait_on_page_bit_killable_timeout(), which is the one I want to use, and out_of_line_wait_on_bit_timeout() which is a reasonably general example. Others can be added as needed. Acked-by: Peter Zijlstra (Intel) Signed-off-by: NeilBrown Acked-by: Ingo Molnar Signed-off-by: Trond Myklebust --- include/linux/wait.h | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) (limited to 'include/linux/wait.h') diff --git a/include/linux/wait.h b/include/linux/wait.h index 6fb1ba5f9b2f..80115bf88671 100644 --- a/include/linux/wait.h +++ b/include/linux/wait.h @@ -25,7 +25,7 @@ struct wait_bit_key { void *flags; int bit_nr; #define WAIT_ATOMIC_T_BIT_NR -1 - unsigned long private; + unsigned long timeout; }; struct wait_bit_queue { @@ -154,6 +154,7 @@ int __wait_on_bit_lock(wait_queue_head_t *, struct wait_bit_queue *, wait_bit_ac void wake_up_bit(void *, int); void wake_up_atomic_t(atomic_t *); int out_of_line_wait_on_bit(void *, int, wait_bit_action_f *, unsigned); +int out_of_line_wait_on_bit_timeout(void *, int, wait_bit_action_f *, unsigned, unsigned long); int out_of_line_wait_on_bit_lock(void *, int, wait_bit_action_f *, unsigned); int out_of_line_wait_on_atomic_t(atomic_t *, int (*)(atomic_t *), unsigned); wait_queue_head_t *bit_waitqueue(void *, int); @@ -859,6 +860,8 @@ int wake_bit_function(wait_queue_t *wait, unsigned mode, int sync, void *key); extern int bit_wait(struct wait_bit_key *); extern int bit_wait_io(struct wait_bit_key *); +extern int bit_wait_timeout(struct wait_bit_key *); +extern int bit_wait_io_timeout(struct wait_bit_key *); /** * wait_on_bit - wait for a bit to be cleared -- cgit v1.2.1 From 61ada528dea028331e99e8ceaed87c683ad25de2 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Wed, 24 Sep 2014 10:18:47 +0200 Subject: sched/wait: Provide infrastructure to deal with nested blocking There are a few places that call blocking primitives from wait loops, provide infrastructure to support this without the typical task_struct::state collision. We record the wakeup in wait_queue_t::flags which leaves task_struct::state free to be used by others. Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Oleg Nesterov Cc: tglx@linutronix.de Cc: ilya.dryomov@inktank.com Cc: umgwanakikbuti@gmail.com Cc: Linus Torvalds Link: http://lkml.kernel.org/r/20140924082242.051202318@infradead.org Signed-off-by: Ingo Molnar --- include/linux/wait.h | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) (limited to 'include/linux/wait.h') diff --git a/include/linux/wait.h b/include/linux/wait.h index e4a8eb9312ea..fc0e99395fbb 100644 --- a/include/linux/wait.h +++ b/include/linux/wait.h @@ -13,9 +13,12 @@ typedef struct __wait_queue wait_queue_t; typedef int (*wait_queue_func_t)(wait_queue_t *wait, unsigned mode, int flags, void *key); int default_wake_function(wait_queue_t *wait, unsigned mode, int flags, void *key); +/* __wait_queue::flags */ +#define WQ_FLAG_EXCLUSIVE 0x01 +#define WQ_FLAG_WOKEN 0x02 + struct __wait_queue { unsigned int flags; -#define WQ_FLAG_EXCLUSIVE 0x01 void *private; wait_queue_func_t func; struct list_head task_list; @@ -830,6 +833,8 @@ void prepare_to_wait_exclusive(wait_queue_head_t *q, wait_queue_t *wait, int sta long prepare_to_wait_event(wait_queue_head_t *q, wait_queue_t *wait, int state); void finish_wait(wait_queue_head_t *q, wait_queue_t *wait); void abort_exclusive_wait(wait_queue_head_t *q, wait_queue_t *wait, unsigned int mode, void *key); +long wait_woken(wait_queue_t *wait, unsigned mode, long timeout); +int woken_wake_function(wait_queue_t *wait, unsigned mode, int sync, void *key); int autoremove_wake_function(wait_queue_t *wait, unsigned mode, int sync, void *key); int wake_bit_function(wait_queue_t *wait, unsigned mode, int sync, void *key); -- cgit v1.2.1 From e22b886a8a43b147e1994a9f970f678fc0df2033 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Wed, 24 Sep 2014 10:18:48 +0200 Subject: sched/wait: Add might_sleep() checks Add more might_sleep() checks, suppose someone put a wait_event() like thing in a wait loop.. Can't put might_sleep() in ___wait_event() because there's the locked primitives which call ___wait_event() with locks held. Signed-off-by: Peter Zijlstra (Intel) Cc: tglx@linutronix.de Cc: ilya.dryomov@inktank.com Cc: umgwanakikbuti@gmail.com Cc: Oleg Nesterov Cc: Linus Torvalds Link: http://lkml.kernel.org/r/20140924082242.119255706@infradead.org Signed-off-by: Ingo Molnar --- include/linux/wait.h | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) (limited to 'include/linux/wait.h') diff --git a/include/linux/wait.h b/include/linux/wait.h index fc0e99395fbb..0421775e0b9f 100644 --- a/include/linux/wait.h +++ b/include/linux/wait.h @@ -261,6 +261,7 @@ __out: __ret; \ */ #define wait_event(wq, condition) \ do { \ + might_sleep(); \ if (condition) \ break; \ __wait_event(wq, condition); \ @@ -293,6 +294,7 @@ do { \ #define wait_event_timeout(wq, condition, timeout) \ ({ \ long __ret = timeout; \ + might_sleep(); \ if (!___wait_cond_timeout(condition)) \ __ret = __wait_event_timeout(wq, condition, timeout); \ __ret; \ @@ -318,6 +320,7 @@ do { \ */ #define wait_event_cmd(wq, condition, cmd1, cmd2) \ do { \ + might_sleep(); \ if (condition) \ break; \ __wait_event_cmd(wq, condition, cmd1, cmd2); \ @@ -345,6 +348,7 @@ do { \ #define wait_event_interruptible(wq, condition) \ ({ \ int __ret = 0; \ + might_sleep(); \ if (!(condition)) \ __ret = __wait_event_interruptible(wq, condition); \ __ret; \ @@ -378,6 +382,7 @@ do { \ #define wait_event_interruptible_timeout(wq, condition, timeout) \ ({ \ long __ret = timeout; \ + might_sleep(); \ if (!___wait_cond_timeout(condition)) \ __ret = __wait_event_interruptible_timeout(wq, \ condition, timeout); \ @@ -428,6 +433,7 @@ do { \ #define wait_event_hrtimeout(wq, condition, timeout) \ ({ \ int __ret = 0; \ + might_sleep(); \ if (!(condition)) \ __ret = __wait_event_hrtimeout(wq, condition, timeout, \ TASK_UNINTERRUPTIBLE); \ @@ -453,6 +459,7 @@ do { \ #define wait_event_interruptible_hrtimeout(wq, condition, timeout) \ ({ \ long __ret = 0; \ + might_sleep(); \ if (!(condition)) \ __ret = __wait_event_hrtimeout(wq, condition, timeout, \ TASK_INTERRUPTIBLE); \ @@ -466,6 +473,7 @@ do { \ #define wait_event_interruptible_exclusive(wq, condition) \ ({ \ int __ret = 0; \ + might_sleep(); \ if (!(condition)) \ __ret = __wait_event_interruptible_exclusive(wq, condition);\ __ret; \ @@ -640,6 +648,7 @@ do { \ #define wait_event_killable(wq, condition) \ ({ \ int __ret = 0; \ + might_sleep(); \ if (!(condition)) \ __ret = __wait_event_killable(wq, condition); \ __ret; \ @@ -891,6 +900,7 @@ extern int bit_wait_io_timeout(struct wait_bit_key *); static inline int wait_on_bit(void *word, int bit, unsigned mode) { + might_sleep(); if (!test_bit(bit, word)) return 0; return out_of_line_wait_on_bit(word, bit, @@ -915,6 +925,7 @@ wait_on_bit(void *word, int bit, unsigned mode) static inline int wait_on_bit_io(void *word, int bit, unsigned mode) { + might_sleep(); if (!test_bit(bit, word)) return 0; return out_of_line_wait_on_bit(word, bit, @@ -941,6 +952,7 @@ wait_on_bit_io(void *word, int bit, unsigned mode) static inline int wait_on_bit_action(void *word, int bit, wait_bit_action_f *action, unsigned mode) { + might_sleep(); if (!test_bit(bit, word)) return 0; return out_of_line_wait_on_bit(word, bit, action, mode); @@ -968,6 +980,7 @@ wait_on_bit_action(void *word, int bit, wait_bit_action_f *action, unsigned mode static inline int wait_on_bit_lock(void *word, int bit, unsigned mode) { + might_sleep(); if (!test_and_set_bit(bit, word)) return 0; return out_of_line_wait_on_bit_lock(word, bit, bit_wait, mode); @@ -991,6 +1004,7 @@ wait_on_bit_lock(void *word, int bit, unsigned mode) static inline int wait_on_bit_lock_io(void *word, int bit, unsigned mode) { + might_sleep(); if (!test_and_set_bit(bit, word)) return 0; return out_of_line_wait_on_bit_lock(word, bit, bit_wait_io, mode); @@ -1016,6 +1030,7 @@ wait_on_bit_lock_io(void *word, int bit, unsigned mode) static inline int wait_on_bit_lock_action(void *word, int bit, wait_bit_action_f *action, unsigned mode) { + might_sleep(); if (!test_and_set_bit(bit, word)) return 0; return out_of_line_wait_on_bit_lock(word, bit, action, mode); @@ -1034,6 +1049,7 @@ wait_on_bit_lock_action(void *word, int bit, wait_bit_action_f *action, unsigned static inline int wait_on_atomic_t(atomic_t *val, int (*action)(atomic_t *), unsigned mode) { + might_sleep(); if (atomic_read(val) == 0) return 0; return out_of_line_wait_on_atomic_t(val, action, mode); -- cgit v1.2.1 From 36df04bc5273a046f53b5e359febc1225f85aa7b Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Wed, 29 Oct 2014 12:21:57 +0100 Subject: sched/wait: Reimplement wait_event_freezable() Provide better implementations of wait_event_freezable() APIs. The problem is with freezer_do_not_count(), it hides the thread from the freezer, even though this thread might not actually freeze/sleep at all. Cc: oleg@redhat.com Cc: Rafael Wysocki Signed-off-by: Peter Zijlstra (Intel) Cc: Len Brown Cc: Linus Torvalds Cc: Pavel Machek Cc: Rafael J. Wysocki Cc: linux-pm@vger.kernel.org Link: http://lkml.kernel.org/n/tip-d86fz1jmso9wjxa8jfpinp8o@git.kernel.org Signed-off-by: Ingo Molnar --- include/linux/wait.h | 57 ++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 57 insertions(+) (limited to 'include/linux/wait.h') diff --git a/include/linux/wait.h b/include/linux/wait.h index 0421775e0b9f..2232ed16635a 100644 --- a/include/linux/wait.h +++ b/include/linux/wait.h @@ -267,6 +267,31 @@ do { \ __wait_event(wq, condition); \ } while (0) +#define __wait_event_freezable(wq, condition) \ + ___wait_event(wq, condition, TASK_INTERRUPTIBLE, 0, 0, \ + schedule(); try_to_freeze()) + +/** + * wait_event - sleep (or freeze) until a condition gets true + * @wq: the waitqueue to wait on + * @condition: a C expression for the event to wait for + * + * The process is put to sleep (TASK_INTERRUPTIBLE -- so as not to contribute + * to system load) until the @condition evaluates to true. The + * @condition is checked each time the waitqueue @wq is woken up. + * + * wake_up() has to be called after changing any variable that could + * change the result of the wait condition. + */ +#define wait_event_freezable(wq, condition) \ +({ \ + int __ret = 0; \ + might_sleep(); \ + if (!(condition)) \ + __ret = __wait_event_freezable(wq, condition); \ + __ret; \ +}) + #define __wait_event_timeout(wq, condition, timeout) \ ___wait_event(wq, ___wait_cond_timeout(condition), \ TASK_UNINTERRUPTIBLE, 0, timeout, \ @@ -300,6 +325,24 @@ do { \ __ret; \ }) +#define __wait_event_freezable_timeout(wq, condition, timeout) \ + ___wait_event(wq, ___wait_cond_timeout(condition), \ + TASK_INTERRUPTIBLE, 0, timeout, \ + __ret = schedule_timeout(__ret); try_to_freeze()) + +/* + * like wait_event_timeout() -- except it uses TASK_INTERRUPTIBLE to avoid + * increasing load and is freezable. + */ +#define wait_event_freezable_timeout(wq, condition, timeout) \ +({ \ + long __ret = timeout; \ + might_sleep(); \ + if (!___wait_cond_timeout(condition)) \ + __ret = __wait_event_freezable_timeout(wq, condition, timeout); \ + __ret; \ +}) + #define __wait_event_cmd(wq, condition, cmd1, cmd2) \ (void)___wait_event(wq, condition, TASK_UNINTERRUPTIBLE, 0, 0, \ cmd1; schedule(); cmd2) @@ -480,6 +523,20 @@ do { \ }) +#define __wait_event_freezable_exclusive(wq, condition) \ + ___wait_event(wq, condition, TASK_INTERRUPTIBLE, 1, 0, \ + schedule(); try_to_freeze()) + +#define wait_event_freezable_exclusive(wq, condition) \ +({ \ + int __ret = 0; \ + might_sleep(); \ + if (!(condition)) \ + __ret = __wait_event_freezable_exclusive(wq, condition);\ + __ret; \ +}) + + #define __wait_event_interruptible_locked(wq, condition, exclusive, irq) \ ({ \ int __ret = 0; \ -- cgit v1.2.1