diff options
author | Paolo Bonzini <pbonzini@redhat.com> | 2017-01-12 19:07:59 +0100 |
---|---|---|
committer | Stefan Hajnoczi <stefanha@redhat.com> | 2017-01-16 13:25:18 +0000 |
commit | 7c690fd1931f0908b18f7034b5d71d7b27ca59ef (patch) | |
tree | fdc01d4b37919eb554fa3ed65d54138694f9ed58 /include | |
parent | b92d9a91abae1569ac499f72fbb90ee7b0ae5398 (diff) |
aio: document locking
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Message-id: 20170112180800.21085-10-pbonzini@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Diffstat (limited to 'include')
-rw-r--r-- | include/block/aio.h | 32 |
1 files changed, 16 insertions, 16 deletions
diff --git a/include/block/aio.h b/include/block/aio.h index be3adfec43..7df271d2b9 100644 --- a/include/block/aio.h +++ b/include/block/aio.h @@ -53,18 +53,12 @@ struct LinuxAioState; struct AioContext { GSource source; - /* Protects all fields from multi-threaded access */ + /* Used by AioContext users to protect from multi-threaded access. */ QemuRecMutex lock; - /* The list of registered AIO handlers */ + /* The list of registered AIO handlers. Protected by ctx->list_lock. */ QLIST_HEAD(, AioHandler) aio_handlers; - /* This is a simple lock used to protect the aio_handlers list. - * Specifically, it's used to ensure that no callbacks are removed while - * we're walking and dispatching callbacks. - */ - int walking_handlers; - /* Used to avoid unnecessary event_notifier_set calls in aio_notify; * accessed with atomic primitives. If this field is 0, everything * (file descriptors, bottom halves, timers) will be re-evaluated @@ -90,9 +84,9 @@ struct AioContext { */ uint32_t notify_me; - /* A lock to protect between bh's adders and deleter, and to ensure - * that no callbacks are removed while we're walking and dispatching - * them. + /* A lock to protect between QEMUBH and AioHandler adders and deleter, + * and to ensure that no callbacks are removed while we're walking and + * dispatching them. */ QemuLockCnt list_lock; @@ -114,7 +108,9 @@ struct AioContext { bool notified; EventNotifier notifier; - /* Thread pool for performing work and receiving completion callbacks */ + /* Thread pool for performing work and receiving completion callbacks. + * Has its own locking. + */ struct ThreadPool *thread_pool; #ifdef CONFIG_LINUX_AIO @@ -124,7 +120,9 @@ struct AioContext { struct LinuxAioState *linux_aio; #endif - /* TimerLists for calling timers - one per clock type */ + /* TimerLists for calling timers - one per clock type. Has its own + * locking. + */ QEMUTimerListGroup tlg; int external_disable_cnt; @@ -178,9 +176,11 @@ void aio_context_unref(AioContext *ctx); * automatically takes care of calling aio_context_acquire and * aio_context_release. * - * Access to timers and BHs from a thread that has not acquired AioContext - * is possible. Access to callbacks for now must be done while the AioContext - * is owned by the thread (FIXME). + * Note that this is separate from bdrv_drained_begin/bdrv_drained_end. A + * thread still has to call those to avoid being interrupted by the guest. + * + * Bottom halves, timers and callbacks can be created or removed without + * acquiring the AioContext. */ void aio_context_acquire(AioContext *ctx); |