From 0f08586c7171757d77c27ee6c606e8a1c44ac6e3 Mon Sep 17 00:00:00 2001 From: Stefan Hajnoczi Date: Wed, 14 Apr 2021 21:02:46 +0100 Subject: util/async: add a human-readable name to BHs for debugging MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit It can be difficult to debug issues with BHs in production environments. Although BHs can usually be identified by looking up their ->cb() function pointer, this requires debug information for the program. It is also not possible to print human-readable diagnostics about BHs because they have no identifier. This patch adds a name to each BH. The name is not unique per instance but differentiates between cb() functions, which is usually enough. It's done by changing aio_bh_new() and friends to macros that stringify cb. The next patch will use the name field when reporting leaked BHs. Signed-off-by: Stefan Hajnoczi Reviewed-by: Philippe Mathieu-Daudé Message-Id: <20210414200247.917496-2-stefanha@redhat.com> --- include/block/aio.h | 31 ++++++++++++++++++++++++++++--- include/qemu/main-loop.h | 4 +++- tests/unit/ptimer-test-stubs.c | 2 +- util/async.c | 9 +++++++-- util/main-loop.c | 4 ++-- 5 files changed, 41 insertions(+), 9 deletions(-) diff --git a/include/block/aio.h b/include/block/aio.h index 10fcae1515..807edce9b5 100644 --- a/include/block/aio.h +++ b/include/block/aio.h @@ -291,20 +291,45 @@ void aio_context_acquire(AioContext *ctx); /* Relinquish ownership of the AioContext. */ void aio_context_release(AioContext *ctx); +/** + * aio_bh_schedule_oneshot_full: Allocate a new bottom half structure that will + * run only once and as soon as possible. + * + * @name: A human-readable identifier for debugging purposes. + */ +void aio_bh_schedule_oneshot_full(AioContext *ctx, QEMUBHFunc *cb, void *opaque, + const char *name); + /** * aio_bh_schedule_oneshot: Allocate a new bottom half structure that will run * only once and as soon as possible. + * + * A convenience wrapper for aio_bh_schedule_oneshot_full() that uses cb as the + * name string. */ -void aio_bh_schedule_oneshot(AioContext *ctx, QEMUBHFunc *cb, void *opaque); +#define aio_bh_schedule_oneshot(ctx, cb, opaque) \ + aio_bh_schedule_oneshot_full((ctx), (cb), (opaque), (stringify(cb))) /** - * aio_bh_new: Allocate a new bottom half structure. + * aio_bh_new_full: Allocate a new bottom half structure. * * Bottom halves are lightweight callbacks whose invocation is guaranteed * to be wait-free, thread-safe and signal-safe. The #QEMUBH structure * is opaque and must be allocated prior to its use. + * + * @name: A human-readable identifier for debugging purposes. + */ +QEMUBH *aio_bh_new_full(AioContext *ctx, QEMUBHFunc *cb, void *opaque, + const char *name); + +/** + * aio_bh_new: Allocate a new bottom half structure + * + * A convenience wrapper for aio_bh_new_full() that uses the cb as the name + * string. */ -QEMUBH *aio_bh_new(AioContext *ctx, QEMUBHFunc *cb, void *opaque); +#define aio_bh_new(ctx, cb, opaque) \ + aio_bh_new_full((ctx), (cb), (opaque), (stringify(cb))) /** * aio_notify: Force processing of pending events. diff --git a/include/qemu/main-loop.h b/include/qemu/main-loop.h index 98aef5647c..8dbc6fcb89 100644 --- a/include/qemu/main-loop.h +++ b/include/qemu/main-loop.h @@ -294,7 +294,9 @@ void qemu_cond_timedwait_iothread(QemuCond *cond, int ms); void qemu_fd_register(int fd); -QEMUBH *qemu_bh_new(QEMUBHFunc *cb, void *opaque); +#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); 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 7f801a4d09..2a3ef58799 100644 --- a/tests/unit/ptimer-test-stubs.c +++ b/tests/unit/ptimer-test-stubs.c @@ -108,7 +108,7 @@ int64_t qemu_clock_deadline_ns_all(QEMUClockType type, int attr_mask) return deadline; } -QEMUBH *qemu_bh_new(QEMUBHFunc *cb, void *opaque) +QEMUBH *qemu_bh_new_full(QEMUBHFunc *cb, void *opaque, const char *name) { QEMUBH *bh = g_new(QEMUBH, 1); diff --git a/util/async.c b/util/async.c index 5d9b7cc1eb..9a668996b8 100644 --- a/util/async.c +++ b/util/async.c @@ -57,6 +57,7 @@ enum { struct QEMUBH { AioContext *ctx; + const char *name; QEMUBHFunc *cb; void *opaque; QSLIST_ENTRY(QEMUBH) next; @@ -107,7 +108,8 @@ static QEMUBH *aio_bh_dequeue(BHList *head, unsigned *flags) return bh; } -void aio_bh_schedule_oneshot(AioContext *ctx, QEMUBHFunc *cb, void *opaque) +void aio_bh_schedule_oneshot_full(AioContext *ctx, QEMUBHFunc *cb, + void *opaque, const char *name) { QEMUBH *bh; bh = g_new(QEMUBH, 1); @@ -115,11 +117,13 @@ void aio_bh_schedule_oneshot(AioContext *ctx, QEMUBHFunc *cb, void *opaque) .ctx = ctx, .cb = cb, .opaque = opaque, + .name = name, }; aio_bh_enqueue(bh, BH_SCHEDULED | BH_ONESHOT); } -QEMUBH *aio_bh_new(AioContext *ctx, QEMUBHFunc *cb, void *opaque) +QEMUBH *aio_bh_new_full(AioContext *ctx, QEMUBHFunc *cb, void *opaque, + const char *name) { QEMUBH *bh; bh = g_new(QEMUBH, 1); @@ -127,6 +131,7 @@ QEMUBH *aio_bh_new(AioContext *ctx, QEMUBHFunc *cb, void *opaque) .ctx = ctx, .cb = cb, .opaque = opaque, + .name = name, }; return bh; } diff --git a/util/main-loop.c b/util/main-loop.c index 4ae5b23e99..06b18b195c 100644 --- a/util/main-loop.c +++ b/util/main-loop.c @@ -544,9 +544,9 @@ void main_loop_wait(int nonblocking) /* Functions to operate on the main QEMU AioContext. */ -QEMUBH *qemu_bh_new(QEMUBHFunc *cb, void *opaque) +QEMUBH *qemu_bh_new_full(QEMUBHFunc *cb, void *opaque, const char *name) { - return aio_bh_new(qemu_aio_context, cb, opaque); + return aio_bh_new_full(qemu_aio_context, cb, opaque, name); } /* -- cgit v1.2.3