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async: Add an optional reentrancy guard to the BH API

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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 <alxndr@bu.edu>
Reviewed-by: Darren Kenny <darren.kenny@oracle.com>
Message-Id: <20230427211013.2994127-3-alxndr@bu.edu>
[thuth: Fix "line over 90 characters" checkpatch.pl error]
Signed-off-by: Thomas Huth <thuth@redhat.com>
This commit is contained in:
Alexander Bulekov 2023-04-27 17:10:07 -04:00 • committed by Thomas Huth
parent a2e1753b80
commit 9c86c97f12
7 changed files with 52 additions and 8 deletions
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18
util/async.c
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@ -65,6 +65,7 @@ struct QEMUBH {
void *opaque;
QSLIST_ENTRY(QEMUBH) next;
unsigned flags;
MemReentrancyGuard *reentrancy_guard;
};
/* Called concurrently from any thread */
@ -137,7 +138,7 @@ 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);
@ -146,13 +147,28 @@ 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)
{
bool last_engaged_in_io = false;
if (bh->reentrancy_guard) {
last_engaged_in_io = bh->reentrancy_guard->engaged_in_io;
if (bh->reentrancy_guard->engaged_in_io) {
trace_reentrant_aio(bh->ctx, bh->name);
}
bh->reentrancy_guard->engaged_in_io = true;
}
bh->cb(bh->opaque);
if (bh->reentrancy_guard) {
bh->reentrancy_guard->engaged_in_io = last_engaged_in_io;
}
}
/* Multiple occurrences of aio_bh_poll cannot be called concurrently. */