BH and fd handler APIs need to know which AioContext (event loop) to run inside. Passing it around everywhere is not feasible since it would require adding arguments to any call-chain that invokes BH and fd handler APIs (hint: there are many and they change).
Instead make the AioContext pointer thread-local. This way, any function that needs to use an AioContext can find it. In particular: the iothread and vcpu threads share the main AioContext since they hold the global mutex while running. Dataplane threads will use their own AioContexts. Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com> --- async.c | 2 ++ cpus.c | 2 ++ include/block/aio.h | 4 ++++ main-loop.c | 1 + 4 files changed, 9 insertions(+) diff --git a/async.c b/async.c index 90fe906..765cbc0 100644 --- a/async.c +++ b/async.c @@ -27,6 +27,8 @@ #include "block/thread-pool.h" #include "qemu/main-loop.h" +DEFINE_TLS(AioContext*, thread_aio_context); + /***********************************************************/ /* bottom halves (can be seen as timers which expire ASAP) */ diff --git a/cpus.c b/cpus.c index c232265..529d612 100644 --- a/cpus.c +++ b/cpus.c @@ -741,6 +741,7 @@ static void *qemu_kvm_cpu_thread_fn(void *arg) qemu_thread_get_self(cpu->thread); cpu->thread_id = qemu_get_thread_id(); cpu_single_env = env; + *alloc_thread_aio_context() = qemu_get_aio_context(); r = kvm_init_vcpu(cpu); if (r < 0) { @@ -815,6 +816,7 @@ static void tcg_exec_all(void); static void tcg_signal_cpu_creation(CPUState *cpu, void *data) { cpu->thread_id = qemu_get_thread_id(); + *alloc_thread_aio_context() = qemu_get_aio_context(); cpu->created = true; } diff --git a/include/block/aio.h b/include/block/aio.h index 1836793..6ee9369 100644 --- a/include/block/aio.h +++ b/include/block/aio.h @@ -17,6 +17,7 @@ #include "qemu-common.h" #include "qemu/queue.h" #include "qemu/event_notifier.h" +#include "qemu/tls.h" typedef struct BlockDriverAIOCB BlockDriverAIOCB; typedef void BlockDriverCompletionFunc(void *opaque, int ret); @@ -74,6 +75,9 @@ typedef struct AioContext { /* Returns 1 if there are still outstanding AIO requests; 0 otherwise */ typedef int (AioFlushEventNotifierHandler)(EventNotifier *e); +/* Each thread can have a default AioContext */ +DECLARE_TLS(AioContext*, thread_aio_context); + /** * aio_context_new: Allocate a new AioContext. * diff --git a/main-loop.c b/main-loop.c index cf36645..51eeb0f 100644 --- a/main-loop.c +++ b/main-loop.c @@ -142,6 +142,7 @@ int qemu_init_main_loop(void) gpollfds = g_array_new(FALSE, FALSE, sizeof(GPollFD)); qemu_aio_context = aio_context_new(); + *get_thread_aio_context() = qemu_aio_context; src = aio_get_g_source(qemu_aio_context); g_source_attach(src, NULL); g_source_unref(src); -- 1.8.1.4