Messages in this thread Patch in this message | | | Date | Wed, 11 Dec 2002 21:04:51 -0800 | From | David Brownell <> | Subject | [patch 2.5.51] add wait_event() to <linux/completion.h> |
| |
Folk periodically talk about evolving the "struct completion" support ... here's one:
int wait_event (struct completion *x, signed long timeout_jiffies);
Returns zero if the event happened, nonzero if it timed out. An example timeout action might be to cancel a request then use wait_for_completion(x) to synchronize with that.
It's been behaving for me so far. Questions from me:
- Is this appropriate to merge as-is? The tradeoff I'm thinking of is code duplication; this patch avoids it ("smaller==better" rule-of-thumb) but maybe someone has real tuning knowledge, or a "standard" lk policy applies. Or there might be bugs or api transgressions.
- One routine was unavailable to modules; now exported. That seemed to just be an oversight.
This doesn't add an "interruptible wait" api mode, which I'd expect some others might find a use for. This patch will let us clean up some dubious code in usbcore which is more or less trying to do a wait_event().
Thanks in advance for any comments.
- Dave --- ./include/linux-dist/completion.h Sun Dec 8 10:57:47 2002 +++ ./include/linux/completion.h Mon Dec 9 15:11:51 2002 @@ -28,6 +28,7 @@ } extern void FASTCALL(wait_for_completion(struct completion *)); +extern int FASTCALL(wait_timeout(struct completion *, signed long jiffies)); extern void FASTCALL(complete(struct completion *)); extern void FASTCALL(complete_all(struct completion *)); --- ./kernel-dist/ksyms.c Sun Dec 8 10:57:48 2002 +++ ./kernel/ksyms.c Mon Dec 9 15:13:47 2002 @@ -404,7 +404,9 @@ EXPORT_SYMBOL(autoremove_wake_function); /* completion handling */ EXPORT_SYMBOL(wait_for_completion); +EXPORT_SYMBOL(wait_timeout); EXPORT_SYMBOL(complete); +EXPORT_SYMBOL(complete_all); /* The notion of irq probe/assignment is foreign to S/390 */ --- ./kernel-dist/sched.c Sun Dec 8 10:57:48 2002 +++ ./kernel/sched.c Mon Dec 9 15:34:36 2002 @@ -1204,6 +1204,11 @@ void complete_all(struct completion *x) void wait_for_completion(struct completion *x) { + wait_timeout (x, MAX_SCHEDULE_TIMEOUT); +} + +int wait_timeout(struct completion *x, signed long timeout_jiffies) +{ might_sleep(); spin_lock_irq(&x->wait.lock); if (!x->done) { @@ -1214,13 +1219,19 @@ void wait_for_completion(struct completi do { __set_current_state(TASK_UNINTERRUPTIBLE); spin_unlock_irq(&x->wait.lock); - schedule(); + timeout_jiffies = schedule_timeout(timeout_jiffies); + if (timeout_jiffies == 0) { + __remove_wait_queue(&x->wait, &wait); + /* caller should wait again */ + return 1; + } spin_lock_irq(&x->wait.lock); } while (!x->done); __remove_wait_queue(&x->wait, &wait); } x->done--; spin_unlock_irq(&x->wait.lock); + return 0; } #define SLEEP_ON_VAR \ | |