From: Paolo Bonzini <pbonzini@redhat.com>
To: qemu-devel@nongnu.org
Cc: John Snow <jsnow@redhat.com>
Subject: [Qemu-devel] [PATCH] dma-helpers: ensure AIO callback is invoked after cancellation
Date: Mon, 29 Jul 2019 23:34:16 +0200 [thread overview]
Message-ID: <20190729213416.1972-1-pbonzini@redhat.com> (raw)
dma_aio_cancel unschedules the BH if there is one, which corresponds
to the reschedule_dma case of dma_blk_cb. This can stall the DMA
permanently, because dma_complete will never get invoked and therefore
nobody will ever invoke the original AIO callback in dbs->common.cb.
Fix this by invoking the callback (which is ensured to happen after
a bdrv_aio_cancel_async, or done manually in the dbs->bh case), and
add assertions to check that the DMA state machine is indeed waiting
for dma_complete or reschedule_dma, but never both.
Reported-by: John Snow <jsnow@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
dma-helpers.c | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)
diff --git a/dma-helpers.c b/dma-helpers.c
index 2d7e02d..d3871dc 100644
--- a/dma-helpers.c
+++ b/dma-helpers.c
@@ -90,6 +90,7 @@ static void reschedule_dma(void *opaque)
{
DMAAIOCB *dbs = (DMAAIOCB *)opaque;
+ assert(!dbs->acb && dbs->bh);
qemu_bh_delete(dbs->bh);
dbs->bh = NULL;
dma_blk_cb(dbs, 0);
@@ -111,15 +112,12 @@ static void dma_complete(DMAAIOCB *dbs, int ret)
{
trace_dma_complete(dbs, ret, dbs->common.cb);
+ assert(!dbs->acb && !dbs->bh);
dma_blk_unmap(dbs);
if (dbs->common.cb) {
dbs->common.cb(dbs->common.opaque, ret);
}
qemu_iovec_destroy(&dbs->iov);
- if (dbs->bh) {
- qemu_bh_delete(dbs->bh);
- dbs->bh = NULL;
- }
qemu_aio_unref(dbs);
}
@@ -179,14 +177,21 @@ static void dma_aio_cancel(BlockAIOCB *acb)
trace_dma_aio_cancel(dbs);
+ assert(!(dbs->acb && dbs->bh));
if (dbs->acb) {
+ /* This will invoke dma_blk_cb. */
blk_aio_cancel_async(dbs->acb);
+ return;
}
+
if (dbs->bh) {
cpu_unregister_map_client(dbs->bh);
qemu_bh_delete(dbs->bh);
dbs->bh = NULL;
}
+ if (dbs->common.cb) {
+ dbs->common.cb(dbs->common.opaque, -ECANCELED);
+ }
}
static AioContext *dma_get_aio_context(BlockAIOCB *acb)
--
1.8.3.1
next reply other threads:[~2019-07-29 21:35 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-29 21:34 Paolo Bonzini [this message]
2019-07-29 21:46 ` [Qemu-devel] [PATCH] dma-helpers: ensure AIO callback is invoked after cancellation John Snow
2019-07-29 21:51 ` Paolo Bonzini
2019-07-29 22:00 ` John Snow
2019-08-13 22:40 ` John Snow
2019-08-13 22:49 ` John Snow
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