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 f141428..61e86a8 100644
--- a/cpus.c
+++ b/cpus.c
@@ -733,6 +733,7 @@ static void *qemu_kvm_cpu_thread_fn(void *arg)
qemu_thread_get_self(cpu->thread);
cpu->thread_id = qemu_get_thread_id();
current_cpu = cpu;
+ *tls_alloc_thread_aio_context() = qemu_get_aio_context();
r = kvm_init_vcpu(cpu);
if (r < 0) {
@@ -806,6 +807,7 @@ static void tcg_exec_all(void);
static void tcg_signal_cpu_creation(CPUState *cpu, void *data)
{
cpu->thread_id = qemu_get_thread_id();
+ *tls_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 a44fff6..5af3963 100644
--- a/main-loop.c
+++ b/main-loop.c
@@ -143,6 +143,7 @@ int qemu_init_main_loop(void)
gpollfds = g_array_new(FALSE, FALSE, sizeof(GPollFD));
qemu_aio_context = aio_context_new();
+ *tls_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
