From c2cba0ffe495b60c4cc58080281e99c7a6580d4b Mon Sep 17 00:00:00 2001
From: Fam Zheng <famz@redhat.com>
Date: Mon, 16 Mar 2015 17:03:33 +0800
Subject: [PATCH] exec: Atomic access to bounce buffer
There could be a race condition when two processes call
address_space_map concurrently and both want to use the bounce buffer.
Add an in_use flag in BounceBuffer to sync it.
Signed-off-by: Fam Zheng <famz@redhat.com>
Message-Id: <1426496617-10702-2-git-send-email-famz@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
exec.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/exec.c b/exec.c
index 874ecfc2c6..5a1c70085c 100644
--- a/exec.c
+++ b/exec.c
@@ -2482,6 +2482,7 @@ typedef struct {
void *buffer;
hwaddr addr;
hwaddr len;
+ bool in_use;
} BounceBuffer;
static BounceBuffer bounce;
@@ -2570,7 +2571,7 @@ void *address_space_map(AddressSpace *as,
l = len;
mr = address_space_translate(as, addr, &xlat, &l, is_write);
if (!memory_access_is_direct(mr, is_write)) {
- if (bounce.buffer) {
+ if (atomic_xchg(&bounce.in_use, true)) {
return NULL;
}
/* Avoid unbounded allocations */
@@ -2640,6 +2641,7 @@ void address_space_unmap(AddressSpace *as, void *buffer, hwaddr len,
qemu_vfree(bounce.buffer);
bounce.buffer = NULL;
memory_region_unref(bounce.mr);
+ atomic_mb_set(&bounce.in_use, false);
cpu_notify_map_clients();
}
--
2.30.2