diff options
| -rw-r--r-- | block.c | 5 | ||||
| -rw-r--r-- | block/io.c | 10 | ||||
| -rw-r--r-- | include/block/aio-wait.h | 116 | ||||
| -rw-r--r-- | include/block/block.h | 40 | ||||
| -rw-r--r-- | include/block/block_int.h | 7 | ||||
| -rw-r--r-- | util/Makefile.objs | 2 | ||||
| -rw-r--r-- | util/aio-wait.c | 40 |
7 files changed, 174 insertions, 46 deletions
@@ -4716,6 +4716,11 @@ AioContext *bdrv_get_aio_context(BlockDriverState *bs) return bs->aio_context; } +AioWait *bdrv_get_aio_wait(BlockDriverState *bs) +{ + return bs ? &bs->wait : NULL; +} + void bdrv_coroutine_enter(BlockDriverState *bs, Coroutine *co) { aio_co_enter(bdrv_get_aio_context(bs), co); diff --git a/block/io.c b/block/io.c index 4d3d1f640a..2b09c656d0 100644 --- a/block/io.c +++ b/block/io.c @@ -25,6 +25,7 @@ #include "qemu/osdep.h" #include "trace.h" #include "sysemu/block-backend.h" +#include "block/aio-wait.h" #include "block/blockjob.h" #include "block/blockjob_int.h" #include "block/block_int.h" @@ -587,16 +588,9 @@ void bdrv_inc_in_flight(BlockDriverState *bs) atomic_inc(&bs->in_flight); } -static void dummy_bh_cb(void *opaque) -{ -} - void bdrv_wakeup(BlockDriverState *bs) { - /* The barrier (or an atomic op) is in the caller. */ - if (atomic_read(&bs->wakeup)) { - aio_bh_schedule_oneshot(qemu_get_aio_context(), dummy_bh_cb, NULL); - } + aio_wait_kick(bdrv_get_aio_wait(bs)); } void bdrv_dec_in_flight(BlockDriverState *bs) diff --git a/include/block/aio-wait.h b/include/block/aio-wait.h new file mode 100644 index 0000000000..a48c744fa8 --- /dev/null +++ b/include/block/aio-wait.h @@ -0,0 +1,116 @@ +/* + * AioContext wait support + * + * Copyright (C) 2018 Red Hat, Inc. + * + * Permission is hereby granted, free of charge, to any person obtaining a copy + * of this software and associated documentation files (the "Software"), to deal + * in the Software without restriction, including without limitation the rights + * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell + * copies of the Software, and to permit persons to whom the Software is + * furnished to do so, subject to the following conditions: + * + * The above copyright notice and this permission notice shall be included in + * all copies or substantial portions of the Software. + * + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, + * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN + * THE SOFTWARE. + */ + +#ifndef QEMU_AIO_WAIT_H +#define QEMU_AIO_WAIT_H + +#include "block/aio.h" + +/** + * AioWait: + * + * An object that facilitates synchronous waiting on a condition. The main + * loop can wait on an operation running in an IOThread as follows: + * + * AioWait *wait = ...; + * AioContext *ctx = ...; + * MyWork work = { .done = false }; + * schedule_my_work_in_iothread(ctx, &work); + * AIO_WAIT_WHILE(wait, ctx, !work.done); + * + * The IOThread must call aio_wait_kick() to notify the main loop when + * work.done changes: + * + * static void do_work(...) + * { + * ... + * work.done = true; + * aio_wait_kick(wait); + * } + */ +typedef struct { + /* Is the main loop waiting for a kick? Accessed with atomic ops. */ + bool need_kick; +} AioWait; + +/** + * AIO_WAIT_WHILE: + * @wait: the aio wait object + * @ctx: the aio context + * @cond: wait while this conditional expression is true + * + * Wait while a condition is true. Use this to implement synchronous + * operations that require event loop activity. + * + * The caller must be sure that something calls aio_wait_kick() when the value + * of @cond might have changed. + * + * The caller's thread must be the IOThread that owns @ctx or the main loop + * thread (with @ctx acquired exactly once). This function cannot be used to + * wait on conditions between two IOThreads since that could lead to deadlock, + * go via the main loop instead. + */ +#define AIO_WAIT_WHILE(wait, ctx, cond) ({ \ + bool waited_ = false; \ + bool busy_ = true; \ + AioWait *wait_ = (wait); \ + AioContext *ctx_ = (ctx); \ + if (in_aio_context_home_thread(ctx_)) { \ + while ((cond) || busy_) { \ + busy_ = aio_poll(ctx_, (cond)); \ + waited_ |= !!(cond) | busy_; \ + } \ + } else { \ + assert(qemu_get_current_aio_context() == \ + qemu_get_aio_context()); \ + assert(!wait_->need_kick); \ + /* Set wait_->need_kick before evaluating cond. */ \ + atomic_mb_set(&wait_->need_kick, true); \ + while (busy_) { \ + if ((cond)) { \ + waited_ = busy_ = true; \ + aio_context_release(ctx_); \ + aio_poll(qemu_get_aio_context(), true); \ + aio_context_acquire(ctx_); \ + } else { \ + busy_ = aio_poll(ctx_, false); \ + waited_ |= busy_; \ + } \ + } \ + atomic_set(&wait_->need_kick, false); \ + } \ + waited_; }) + +/** + * aio_wait_kick: + * @wait: the aio wait object that should re-evaluate its condition + * + * Wake up the main thread if it is waiting on AIO_WAIT_WHILE(). During + * synchronous operations performed in an IOThread, the main thread lets the + * IOThread's event loop run, waiting for the operation to complete. A + * aio_wait_kick() call will wake up the main thread. + */ +void aio_wait_kick(AioWait *wait); + +#endif /* QEMU_AIO_WAIT */ diff --git a/include/block/block.h b/include/block/block.h index bc41ed253b..4a80a2acd4 100644 --- a/include/block/block.h +++ b/include/block/block.h @@ -2,6 +2,7 @@ #define BLOCK_H #include "block/aio.h" +#include "block/aio-wait.h" #include "qapi-types.h" #include "qemu/iov.h" #include "qemu/coroutine.h" @@ -367,41 +368,14 @@ void bdrv_drain_all_begin(void); void bdrv_drain_all_end(void); void bdrv_drain_all(void); +/* Returns NULL when bs == NULL */ +AioWait *bdrv_get_aio_wait(BlockDriverState *bs); + #define BDRV_POLL_WHILE(bs, cond) ({ \ - bool waited_ = false; \ - bool busy_ = true; \ BlockDriverState *bs_ = (bs); \ - AioContext *ctx_ = bdrv_get_aio_context(bs_); \ - if (in_aio_context_home_thread(ctx_)) { \ - while ((cond) || busy_) { \ - busy_ = aio_poll(ctx_, (cond)); \ - waited_ |= !!(cond) | busy_; \ - } \ - } else { \ - assert(qemu_get_current_aio_context() == \ - qemu_get_aio_context()); \ - /* Ask bdrv_dec_in_flight to wake up the main \ - * QEMU AioContext. Extra I/O threads never take \ - * other I/O threads' AioContexts (see for example \ - * block_job_defer_to_main_loop for how to do it). \ - */ \ - assert(!bs_->wakeup); \ - /* Set bs->wakeup before evaluating cond. */ \ - atomic_mb_set(&bs_->wakeup, true); \ - while (busy_) { \ - if ((cond)) { \ - waited_ = busy_ = true; \ - aio_context_release(ctx_); \ - aio_poll(qemu_get_aio_context(), true); \ - aio_context_acquire(ctx_); \ - } else { \ - busy_ = aio_poll(ctx_, false); \ - waited_ |= busy_; \ - } \ - } \ - atomic_set(&bs_->wakeup, false); \ - } \ - waited_; }) + AIO_WAIT_WHILE(bdrv_get_aio_wait(bs_), \ + bdrv_get_aio_context(bs_), \ + cond); }) int bdrv_pdiscard(BlockDriverState *bs, int64_t offset, int bytes); int bdrv_co_pdiscard(BlockDriverState *bs, int64_t offset, int bytes); diff --git a/include/block/block_int.h b/include/block/block_int.h index 5ae7738cf8..aef10296b0 100644 --- a/include/block/block_int.h +++ b/include/block/block_int.h @@ -26,6 +26,7 @@ #include "block/accounting.h" #include "block/block.h" +#include "block/aio-wait.h" #include "qemu/queue.h" #include "qemu/coroutine.h" #include "qemu/stats64.h" @@ -716,10 +717,8 @@ struct BlockDriverState { unsigned int in_flight; unsigned int serialising_in_flight; - /* Internal to BDRV_POLL_WHILE and bdrv_wakeup. Accessed with atomic - * ops. - */ - bool wakeup; + /* Kicked to signal main loop when a request completes. */ + AioWait wait; /* counter for nested bdrv_io_plug. * Accessed with atomic ops. diff --git a/util/Makefile.objs b/util/Makefile.objs index 3fb611631f..ae90b9963d 100644 --- a/util/Makefile.objs +++ b/util/Makefile.objs @@ -1,7 +1,7 @@ util-obj-y = osdep.o cutils.o unicode.o qemu-timer-common.o util-obj-y += bufferiszero.o util-obj-y += lockcnt.o -util-obj-y += aiocb.o async.o thread-pool.o qemu-timer.o +util-obj-y += aiocb.o async.o aio-wait.o thread-pool.o qemu-timer.o util-obj-y += main-loop.o iohandler.o util-obj-$(CONFIG_POSIX) += aio-posix.o util-obj-$(CONFIG_POSIX) += compatfd.o diff --git a/util/aio-wait.c b/util/aio-wait.c new file mode 100644 index 0000000000..a487cdb852 --- /dev/null +++ b/util/aio-wait.c @@ -0,0 +1,40 @@ +/* + * AioContext wait support + * + * Copyright (C) 2018 Red Hat, Inc. + * + * Permission is hereby granted, free of charge, to any person obtaining a copy + * of this software and associated documentation files (the "Software"), to deal + * in the Software without restriction, including without limitation the rights + * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell + * copies of the Software, and to permit persons to whom the Software is + * furnished to do so, subject to the following conditions: + * + * The above copyright notice and this permission notice shall be included in + * all copies or substantial portions of the Software. + * + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, + * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN + * THE SOFTWARE. + */ + +#include "qemu/osdep.h" +#include "qemu/main-loop.h" +#include "block/aio-wait.h" + +static void dummy_bh_cb(void *opaque) +{ + /* The point is to make AIO_WAIT_WHILE()'s aio_poll() return */ +} + +void aio_wait_kick(AioWait *wait) +{ + /* The barrier (or an atomic op) is in the caller. */ + if (atomic_read(&wait->need_kick)) { + aio_bh_schedule_oneshot(qemu_get_aio_context(), dummy_bh_cb, NULL); + } +} |