Devices can pass their MemoryReentrancyGuard (from their DeviceState), when creating new BHes. Then, the async API will toggle the guard before/after calling the BH call-back. This prevents bh->mmio reentrancy issues.
Signed-off-by: Alexander Bulekov <alx...@bu.edu> --- docs/devel/multiple-iothreads.txt | 2 ++ include/block/aio.h | 18 ++++++++++++++++-- include/qemu/main-loop.h | 7 +++++-- tests/unit/ptimer-test-stubs.c | 3 ++- util/async.c | 12 +++++++++++- util/main-loop.c | 5 +++-- 6 files changed, 39 insertions(+), 8 deletions(-) diff --git a/docs/devel/multiple-iothreads.txt b/docs/devel/multiple-iothreads.txt index 343120f2ef..e4fafed9d9 100644 --- a/docs/devel/multiple-iothreads.txt +++ b/docs/devel/multiple-iothreads.txt @@ -61,6 +61,7 @@ There are several old APIs that use the main loop AioContext: * LEGACY qemu_aio_set_event_notifier() - monitor an event notifier * LEGACY timer_new_ms() - create a timer * LEGACY qemu_bh_new() - create a BH + * LEGACY qemu_bh_new_guarded() - create a BH with a device re-entrancy guard * LEGACY qemu_aio_wait() - run an event loop iteration Since they implicitly work on the main loop they cannot be used in code that @@ -72,6 +73,7 @@ Instead, use the AioContext functions directly (see include/block/aio.h): * aio_set_event_notifier() - monitor an event notifier * aio_timer_new() - create a timer * aio_bh_new() - create a BH + * aio_bh_new_guarded() - create a BH with a device re-entrancy guard * aio_poll() - run an event loop iteration The AioContext can be obtained from the IOThread using diff --git a/include/block/aio.h b/include/block/aio.h index 0f65a3cc9e..94d661ff7e 100644 --- a/include/block/aio.h +++ b/include/block/aio.h @@ -23,6 +23,8 @@ #include "qemu/thread.h" #include "qemu/timer.h" #include "block/graph-lock.h" +#include "hw/qdev-core.h" + typedef struct BlockAIOCB BlockAIOCB; typedef void BlockCompletionFunc(void *opaque, int ret); @@ -332,9 +334,11 @@ void aio_bh_schedule_oneshot_full(AioContext *ctx, QEMUBHFunc *cb, void *opaque, * is opaque and must be allocated prior to its use. * * @name: A human-readable identifier for debugging purposes. + * @reentrancy_guard: A guard set when entering a cb to prevent + * device-reentrancy issues */ QEMUBH *aio_bh_new_full(AioContext *ctx, QEMUBHFunc *cb, void *opaque, - const char *name); + const char *name, MemReentrancyGuard *reentrancy_guard); /** * aio_bh_new: Allocate a new bottom half structure @@ -343,7 +347,17 @@ QEMUBH *aio_bh_new_full(AioContext *ctx, QEMUBHFunc *cb, void *opaque, * string. */ #define aio_bh_new(ctx, cb, opaque) \ - aio_bh_new_full((ctx), (cb), (opaque), (stringify(cb))) + aio_bh_new_full((ctx), (cb), (opaque), (stringify(cb)), NULL) + +/** + * aio_bh_new_guarded: Allocate a new bottom half structure with a + * reentrancy_guard + * + * A convenience wrapper for aio_bh_new_full() that uses the cb as the name + * string. + */ +#define aio_bh_new_guarded(ctx, cb, opaque, guard) \ + aio_bh_new_full((ctx), (cb), (opaque), (stringify(cb)), guard) /** * aio_notify: Force processing of pending events. diff --git a/include/qemu/main-loop.h b/include/qemu/main-loop.h index c25f390696..84d1ce57f0 100644 --- a/include/qemu/main-loop.h +++ b/include/qemu/main-loop.h @@ -389,9 +389,12 @@ void qemu_cond_timedwait_iothread(QemuCond *cond, int ms); void qemu_fd_register(int fd); +#define qemu_bh_new_guarded(cb, opaque, guard) \ + qemu_bh_new_full((cb), (opaque), (stringify(cb)), guard) #define qemu_bh_new(cb, opaque) \ - qemu_bh_new_full((cb), (opaque), (stringify(cb))) -QEMUBH *qemu_bh_new_full(QEMUBHFunc *cb, void *opaque, const char *name); + qemu_bh_new_full((cb), (opaque), (stringify(cb)), NULL) +QEMUBH *qemu_bh_new_full(QEMUBHFunc *cb, void *opaque, const char *name, + MemReentrancyGuard *reentrancy_guard); void qemu_bh_schedule_idle(QEMUBH *bh); enum { diff --git a/tests/unit/ptimer-test-stubs.c b/tests/unit/ptimer-test-stubs.c index f5e75a96b6..24d5413f9d 100644 --- a/tests/unit/ptimer-test-stubs.c +++ b/tests/unit/ptimer-test-stubs.c @@ -107,7 +107,8 @@ int64_t qemu_clock_deadline_ns_all(QEMUClockType type, int attr_mask) return deadline; } -QEMUBH *qemu_bh_new_full(QEMUBHFunc *cb, void *opaque, const char *name) +QEMUBH *qemu_bh_new_full(QEMUBHFunc *cb, void *opaque, const char *name, + MemReentrancyGuard *reentrancy_guard) { QEMUBH *bh = g_new(QEMUBH, 1); diff --git a/util/async.c b/util/async.c index 14d63b3091..08924c3212 100644 --- a/util/async.c +++ b/util/async.c @@ -65,6 +65,7 @@ struct QEMUBH { void *opaque; QSLIST_ENTRY(QEMUBH) next; unsigned flags; + MemReentrancyGuard *reentrancy_guard; }; /* Called concurrently from any thread */ @@ -133,7 +134,7 @@ void aio_bh_schedule_oneshot_full(AioContext *ctx, QEMUBHFunc *cb, } QEMUBH *aio_bh_new_full(AioContext *ctx, QEMUBHFunc *cb, void *opaque, - const char *name) + const char *name, MemReentrancyGuard *reentrancy_guard) { QEMUBH *bh; bh = g_new(QEMUBH, 1); @@ -142,13 +143,22 @@ QEMUBH *aio_bh_new_full(AioContext *ctx, QEMUBHFunc *cb, void *opaque, .cb = cb, .opaque = opaque, .name = name, + .reentrancy_guard = reentrancy_guard, }; return bh; } void aio_bh_call(QEMUBH *bh) { + if (bh->reentrancy_guard) { + bh->reentrancy_guard->engaged_in_io = true; + } + bh->cb(bh->opaque); + + if (bh->reentrancy_guard) { + bh->reentrancy_guard->engaged_in_io = false; + } } /* Multiple occurrences of aio_bh_poll cannot be called concurrently. */ diff --git a/util/main-loop.c b/util/main-loop.c index 58f776a8c9..07d2e2040a 100644 --- a/util/main-loop.c +++ b/util/main-loop.c @@ -617,9 +617,10 @@ void main_loop_wait(int nonblocking) /* Functions to operate on the main QEMU AioContext. */ -QEMUBH *qemu_bh_new_full(QEMUBHFunc *cb, void *opaque, const char *name) +QEMUBH *qemu_bh_new_full(QEMUBHFunc *cb, void *opaque, const char *name, MemReentrancyGuard *reentrancy_guard) { - return aio_bh_new_full(qemu_aio_context, cb, opaque, name); + return aio_bh_new_full(qemu_aio_context, cb, opaque, name, + reentrancy_guard); } /* -- 2.39.0