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From: Stefan Hajnoczi <stefanha@redhat.com>
To: qemu-devel@nongnu.org,
Peter Maydell <peter.maydell@linaro.org>
Subject: [PULL 1/5] util/async: add a human-readable name to BHs for debugging
Date: Thu, 8 Jul 2021 14:11:39 +0100
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Cc: Fam Zheng <fam@euphon.net>, Kevin Wolf <kwolf@redhat.com>,
qemu-block@nongnu.org,
=?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= <philmd@redhat.com>,
Max Reitz <mreitz@redhat.com>, Stefan Hajnoczi <stefanha@redhat.com>,
Paolo Bonzini <pbonzini@redhat.com>, John Snow <jsnow@redhat.com>
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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-Daud=C3=A9 <philmd@redhat.com>
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);
=20
+/**
+ * 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 *o=
paque,
+ 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 a=
s 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)))
=20
/**
- * 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(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)))
=20
/**
* 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 m=
s);
=20
void qemu_fd_register(int fd);
=20
-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);
=20
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;
}
=20
-QEMUBH *qemu_bh_new(QEMUBHFunc *cb, void *opaque)
+QEMUBH *qemu_bh_new_full(QEMUBHFunc *cb, void *opaque, const char *name)
{
QEMUBH *bh =3D g_new(QEMUBH, 1);
=20
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 {
=20
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 *f=
lags)
return bh;
}
=20
-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 =3D g_new(QEMUBH, 1);
@@ -115,11 +117,13 @@ void aio_bh_schedule_oneshot(AioContext *ctx, QEMUBHF=
unc *cb, void *opaque)
.ctx =3D ctx,
.cb =3D cb,
.opaque =3D opaque,
+ .name =3D name,
};
aio_bh_enqueue(bh, BH_SCHEDULED | BH_ONESHOT);
}
=20
-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 =3D g_new(QEMUBH, 1);
@@ -127,6 +131,7 @@ QEMUBH *aio_bh_new(AioContext *ctx, QEMUBHFunc *cb, voi=
d *opaque)
.ctx =3D ctx,
.cb =3D cb,
.opaque =3D opaque,
+ .name =3D 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)
=20
/* Functions to operate on the main QEMU AioContext. */
=20
-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);
}
=20
/*
--=20
2.31.1