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util/async: add a human-readable name to BHs for debugging

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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 <stefanha@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20210414200247.917496-2-stefanha@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2021-04-14 21:02:46 +01:00
parent 711c0418c8
commit 0f08586c71
5 changed files with 43 additions and 11 deletions
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35
include/block/aio.h
View file

@ -292,19 +292,44 @@ void aio_context_acquire(AioContext *ctx);
void aio_context_release(AioContext *ctx);
/**
* aio_bh_schedule_oneshot: Allocate a new bottom half structure that will run
* only once and as soon as possible.
* 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(AioContext *ctx, QEMUBHFunc *cb, void *opaque);
void aio_bh_schedule_oneshot_full(AioContext *ctx, QEMUBHFunc *cb, void *opaque,
const char *name);
/**
* aio_bh_new: Allocate a new bottom half structure.
* 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.
*/
#define aio_bh_schedule_oneshot(ctx, cb, opaque) \
aio_bh_schedule_oneshot_full((ctx), (cb), (opaque), (stringify(cb)))
/**
* 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(AioContext *ctx, QEMUBHFunc *cb, void *opaque);
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.
*/
#define aio_bh_new(ctx, cb, opaque) \
aio_bh_new_full((ctx), (cb), (opaque), (stringify(cb)))
/**
* aio_notify: Force processing of pending events.