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exec: Atomic access to bounce buffer

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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>
This commit is contained in:
Fam Zheng 2015-03-16 17:03:33 +08:00 committed by Paolo Bonzini
parent e3a0abfda7
commit c2cba0ffe4
1 changed files with 3 additions and 1 deletions
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4
exec.c
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@ -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();
}