From 2c977c35d8e44ad21345c3e91088f4f3d3f03605 Mon Sep 17 00:00:00 2001 From: Garrett D'Amore Date: Fri, 1 Sep 2017 10:26:34 -0700 Subject: Add support for synchronous AIO completions. We add a flag (auto-clearing) that can be set on an AIO to indicate that the AIO should not processed asynchronously on a taskq. This can be used to enhance performance in some cases, but it can also be used to permit an AIO be destroyed from a completion callback. (For the latter, the callback must execute the new nni_aio_fini_cb() routine, which destroys the AIO without waiting for it to finish.) --- src/core/aio.h | 22 +++++++++++++++++++++- 1 file changed, 21 insertions(+), 1 deletion(-) (limited to 'src/core/aio.h') diff --git a/src/core/aio.h b/src/core/aio.h index eae17446..717e7995 100644 --- a/src/core/aio.h +++ b/src/core/aio.h @@ -35,7 +35,8 @@ struct nni_aio { unsigned a_active : 1; // aio was started unsigned a_expiring : 1; // expiration callback in progress unsigned a_waiting : 1; // a thread is waiting for this to finish - unsigned a_pad : 26; // ensure 32-bit alignment + unsigned a_synch : 1; // run completion synchronously + unsigned a_pad : 25; // ensure 32-bit alignment nni_task a_task; // Read/write operations. @@ -76,6 +77,12 @@ extern int nni_aio_init(nni_aio **, nni_cb, void *); // on zero'd memory. extern void nni_aio_fini(nni_aio *); +// nni_aio_fini_cb finalizes the aio WITHOUT waiting for it to complete. +// This is intended exclusively for finalizing an AIO from a completion +// callack for that AIO. It is important that the caller ensure that nothing +// else might be waiting for that AIO or using it. +extern void nni_aio_fini_cb(nni_aio *); + // nni_aio_stop cancels any unfinished I/O, running completion callbacks, // but also prevents any new operations from starting (nni_aio_start will // return NNG_ESTATE). This should be called before nni_aio_fini(). The @@ -102,6 +109,19 @@ extern void * nni_aio_get_pipe(nni_aio *); extern void nni_aio_set_ep(nni_aio *, void *); extern void * nni_aio_get_ep(nni_aio *); +// nni_aio_set_synch sets a synchronous completion flag on the AIO. +// When this is set, the next time the AIO is completed, the callback +// be run synchronously, from the thread calling the finish routine. +// It is important that this only be set when the provider knows that +// it is not holding any locks or resources when completing the operation, +// or when the consumer knows that the callback routine does not acquire +// any locks. Use with caution to avoid deadlocks. The flag is cleared +// automatically when the completion callback is executed. Some care has +// been taken so that other aio operations like aio_wait will work, +// although it is still an error to try waiting for an aio from that aio's +// completion callback. +void nni_aio_set_synch(nni_aio *); + // nni_aio_set_timeout sets the timeout (absolute) when the AIO will // be canceled. The cancelation does not happen until after nni_aio_start // is called. -- cgit v1.2.3-70-g09d2