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[Qemu-devel] [PATCH v3 1/4] exec: Atomic access to bounce buffer
From: |
Fam Zheng |
Subject: |
[Qemu-devel] [PATCH v3 1/4] exec: Atomic access to bounce buffer |
Date: |
Mon, 16 Mar 2015 13:31:47 +0800 |
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 <address@hidden>
---
exec.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/exec.c b/exec.c
index e97071a..4080044 100644
--- a/exec.c
+++ b/exec.c
@@ -2483,6 +2483,7 @@ typedef struct {
void *buffer;
hwaddr addr;
hwaddr len;
+ bool in_use;
} BounceBuffer;
static BounceBuffer bounce;
@@ -2571,9 +2572,10 @@ 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;
}
+ smp_mb();
/* Avoid unbounded allocations */
l = MIN(l, TARGET_PAGE_SIZE);
bounce.buffer = qemu_memalign(TARGET_PAGE_SIZE, l);
@@ -2641,6 +2643,7 @@ 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();
}
--
1.9.3