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authorKent Overstreet <koverstreet@google.com>2013-05-07 16:18:43 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2013-05-07 18:38:28 -0700
commit774a08b3548f3f4f36c1a4f2a29a1b3710a2c939 (patch)
treefddb989d580444aaae64a5904f029cc86fe23de9
parent36f5588905c10a8c4568a210d601fe8c3c27e0f0 (diff)
wait: add wait_event_hrtimeout()
Analagous to wait_event_timeout() and friends, this adds wait_event_hrtimeout() and wait_event_interruptible_hrtimeout(). Note that unlike the versions that use regular timers, these don't return the amount of time remaining when they return - instead, they return 0 or -ETIME if they timed out. because I was uncomfortable with the semantics of doing it the other way (that I could get it right, anyways). If the timer expires, there's no real guarantee that expire_time - current_time would be <= 0 - due to timer slack certainly, and I'm not sure I want to know the implications of the different clock bases in hrtimers. If the timer does expire and the code calculates that the time remaining is nonnegative, that could be even worse if the calling code then reuses that timeout. Probably safer to just return 0 then, but I could imagine weird bugs or at least unintended behaviour arising from that too. I came to the conclusion that if other users end up actually needing the amount of time remaining, the sanest thing to do would be to create a version that uses absolute timeouts instead of relative. [akpm@linux-foundation.org: fix description of `timeout' arg] Signed-off-by: Kent Overstreet <koverstreet@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@elte.hu> Cc: Zach Brown <zab@redhat.com> Cc: Felipe Balbi <balbi@ti.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Mark Fasheh <mfasheh@suse.com> Cc: Joel Becker <jlbec@evilplan.org> Cc: Rusty Russell <rusty@rustcorp.com.au> Cc: Jens Axboe <axboe@kernel.dk> Cc: Asai Thambi S P <asamymuthupa@micron.com> Cc: Selvan Mani <smani@micron.com> Cc: Sam Bradshaw <sbradshaw@micron.com> Cc: Jeff Moyer <jmoyer@redhat.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Benjamin LaHaise <bcrl@kvack.org> Reviewed-by: "Theodore Ts'o" <tytso@mit.edu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--include/linux/wait.h86
1 files changed, 86 insertions, 0 deletions
diff --git a/include/linux/wait.h b/include/linux/wait.h
index 7cb64d4b499d..ac38be2692d8 100644
--- a/include/linux/wait.h
+++ b/include/linux/wait.h
@@ -330,6 +330,92 @@ do { \
__ret; \
})
+#define __wait_event_hrtimeout(wq, condition, timeout, state) \
+({ \
+ int __ret = 0; \
+ DEFINE_WAIT(__wait); \
+ struct hrtimer_sleeper __t; \
+ \
+ hrtimer_init_on_stack(&__t.timer, CLOCK_MONOTONIC, \
+ HRTIMER_MODE_REL); \
+ hrtimer_init_sleeper(&__t, current); \
+ if ((timeout).tv64 != KTIME_MAX) \
+ hrtimer_start_range_ns(&__t.timer, timeout, \
+ current->timer_slack_ns, \
+ HRTIMER_MODE_REL); \
+ \
+ for (;;) { \
+ prepare_to_wait(&wq, &__wait, state); \
+ if (condition) \
+ break; \
+ if (state == TASK_INTERRUPTIBLE && \
+ signal_pending(current)) { \
+ __ret = -ERESTARTSYS; \
+ break; \
+ } \
+ if (!__t.task) { \
+ __ret = -ETIME; \
+ break; \
+ } \
+ schedule(); \
+ } \
+ \
+ hrtimer_cancel(&__t.timer); \
+ destroy_hrtimer_on_stack(&__t.timer); \
+ finish_wait(&wq, &__wait); \
+ __ret; \
+})
+
+/**
+ * wait_event_hrtimeout - sleep until a condition gets true or a timeout elapses
+ * @wq: the waitqueue to wait on
+ * @condition: a C expression for the event to wait for
+ * @timeout: timeout, as a ktime_t
+ *
+ * The process is put to sleep (TASK_UNINTERRUPTIBLE) until the
+ * @condition evaluates to true or a signal is received.
+ * 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.
+ *
+ * The function returns 0 if @condition became true, or -ETIME if the timeout
+ * elapsed.
+ */
+#define wait_event_hrtimeout(wq, condition, timeout) \
+({ \
+ int __ret = 0; \
+ if (!(condition)) \
+ __ret = __wait_event_hrtimeout(wq, condition, timeout, \
+ TASK_UNINTERRUPTIBLE); \
+ __ret; \
+})
+
+/**
+ * wait_event_interruptible_hrtimeout - sleep until a condition gets true or a timeout elapses
+ * @wq: the waitqueue to wait on
+ * @condition: a C expression for the event to wait for
+ * @timeout: timeout, as a ktime_t
+ *
+ * The process is put to sleep (TASK_INTERRUPTIBLE) until the
+ * @condition evaluates to true or a signal is received.
+ * 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.
+ *
+ * The function returns 0 if @condition became true, -ERESTARTSYS if it was
+ * interrupted by a signal, or -ETIME if the timeout elapsed.
+ */
+#define wait_event_interruptible_hrtimeout(wq, condition, timeout) \
+({ \
+ long __ret = 0; \
+ if (!(condition)) \
+ __ret = __wait_event_hrtimeout(wq, condition, timeout, \
+ TASK_INTERRUPTIBLE); \
+ __ret; \
+})
+
#define __wait_event_interruptible_exclusive(wq, condition, ret) \
do { \
DEFINE_WAIT(__wait); \