[FFmpeg-cvslog] avutil/fifo: Fix thread saftey of av_fifo_generic_peek()

[Michael Niedermayer]

ffmpeg | branch: master | Michael Niedermayer <michael at niedermayer.cc> | Tue Oct 13 18:29:04 2015 +0200| [147b12162da60da1ebfe38f626e9f82b2102f26b] | committer: Michael Niedermayer

avutil/fifo: Fix thread saftey of av_fifo_generic_peek()

changing the context state and restoring it is not safe if another
thread writes data into the fifo

Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=147b12162da60da1ebfe38f626e9f82b2102f26b
---

 libavutil/fifo.c |   14 ++++++--------
 1 file changed, 6 insertions(+), 8 deletions(-)

diff --git a/libavutil/fifo.c b/libavutil/fifo.c
index 07fb4ec..1a22708 100644
--- a/libavutil/fifo.c
+++ b/libavutil/fifo.c
@@ -153,24 +153,22 @@ int av_fifo_generic_peek(AVFifoBuffer *f, void *dest, int buf_size,
 {
 // Read memory barrier needed for SMP here in theory
     uint8_t *rptr = f->rptr;
-    uint32_t rndx = f->rndx;
 
     do {
-        int len = FFMIN(f->end - f->rptr, buf_size);
+        int len = FFMIN(f->end - rptr, buf_size);
         if (func)
-            func(dest, f->rptr, len);
+            func(dest, rptr, len);
         else {
-            memcpy(dest, f->rptr, len);
+            memcpy(dest, rptr, len);
             dest = (uint8_t *)dest + len;
         }
 // memory barrier needed for SMP here in theory
-        av_fifo_drain(f, len);
+        rptr += len;
+        if (rptr >= f->end)
+            rptr -= f->end - f->buffer;
         buf_size -= len;
     } while (buf_size > 0);
 
-    f->rptr = rptr;
-    f->rndx = rndx;
-
     return 0;
 }