Hi,
On 06.09.2017 03:09, Kenneth Graunke wrote:
Calling exit(1) when execbuffer fails is not necessarily safe.
When running Piglit tests with a Mesa that submitted invalid commands
to the GPU, I discovered the following problem:
1. do_flush_locked fails and calls exit(1)...invoking atexit handlers.
2. Piglit tries to clean up after itself, and does eglMakeCurrent to
release the current context.
3. MakeCurrent calls glFlush (or the internal hook for that)
4. glFlush calls intel_batchbuffer_flush
So we end up trying to flush the batch...in the middle of flushing the
batch...with code that isn't designed to be reentrant. So it breaks
even worse than before. In my case, it just outright crashed.
Calling abort() is probably not what we want either, but it at least
bypasses atexit() handlers, so it won't hit this ugly reentrancy
problem.
If you just want to avoid atexit() handlers, you can use _exit().
That one doesn't trigger ABORT handler.
(Which may be good or bad depending on what you want. I think SDL by
default traps ABORT among many other things, to restore screen mode on
emergency exits.)
- Eero
---
src/mesa/drivers/dri/i965/intel_batchbuffer.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/src/mesa/drivers/dri/i965/intel_batchbuffer.c
b/src/mesa/drivers/dri/i965/intel_batchbuffer.c
index 491aa12dd63..637705226f0 100644
--- a/src/mesa/drivers/dri/i965/intel_batchbuffer.c
+++ b/src/mesa/drivers/dri/i965/intel_batchbuffer.c
@@ -679,7 +679,7 @@ do_flush_locked(struct brw_context *brw, int in_fence_fd,
int *out_fence_fd)
if (ret != 0) {
fprintf(stderr, "intel_do_flush_locked failed: %s\n", strerror(-ret));
- exit(1);
+ abort();
}
return ret;
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