[Mesa-dev] [PATCH] mesa: don't attempt to unlock an unlocked debug state mutex

[Eduardo Lima Mitev]

Looks good.

Reviewed-by: Eduardo Lima Mitev <elima at igalia.com>

On 12/11/2016 04:42 PM, Jonathan Gray wrote:
> Commit 929fcee47e46781c57f2a354ce0a013915c033d1 introduced code that
> attempts to unlock an unlocked mutex which is undefined behaviour.
> 
> On OpenBSD this leads to an abort:
> 
> 0  0x0000124dadfa96ba in thrkill () at <stdin>:2
> 1  0x0000124dadf3da39 in *_libc_abort () at /usr/src/lib/libc/stdlib/abort.c:52
> 2  0x0000124d2c1165b5 in *_libpthread_pthread_mutex_unlock (mutexp=<optimized out>)
>     at /usr/src/lib/librthread/rthread_sync.c:221
> 3  0x0000124d279c02e4 in init_attrib_groups (ctx=0x124df0fda000) at main/context.c:825
> 4  _mesa_initialize_context (ctx=ctx at entry=0x124df0fda000, api=api at entry=API_OPENGL_CORE,
>     visual=visual at entry=0x7f7ffffbdfd0, share_list=share_list at entry=0x0,
>     driverFunctions=driverFunctions at entry=0x7f7ffffbda60) at main/context.c:1204
> 5  0x0000124d27b507ec in st_create_context (api=api at entry=API_OPENGL_CORE,
>     pipe=pipe at entry=0x124dc4910000, visual=visual at entry=0x7f7ffffbdfd0,
>     share=share at entry=0x0, options=options at entry=0x7f7ffffbe128)
>     at state_tracker/st_context.c:545
> 6  0x0000124d27b8639f in st_api_create_context (stapi=<optimized out>,
>     smapi=0x124d1b608800, attribs=0x7f7ffffbe100, error=0x7f7ffffbe0fc, shared_stctxi=0x0)
>     at state_tracker/st_manager.c:669
> 7  0x0000124d27cc5b9c in dri_create_context (api=<optimized out>, visual=0x124d8a0f8a00,
>     cPriv=0x124de473f240, major_version=<optimized out>, minor_version=<optimized out>,
>     flags=<optimized out>, notify_reset=false, error=0x7f7ffffbe2b4,
>     sharedContextPrivate=0x0) at dri_context.c:123
> 8  0x0000124d27cc5029 in driCreateContextAttribs (screen=0x124d8a0f8400,
>     api=<optimized out>, config=0x124d8a0f8a00, shared=<optimized out>,
>     num_attribs=<optimized out>, attribs=<optimized out>, error=0x7f7ffffbe2b4,
>     data=0x124d77814a00) at dri_util.c:448
> 9  0x0000124d8e109b00 in drisw_create_context_attribs (base=0x124df3e08700,
>     config_base=0x124d7a0e7300, shareList=<optimized out>, num_attribs=<optimized out>,
>     attribs=<optimized out>, error=0x7f7ffffbe2b4) at drisw_glx.c:476
> 10 0x0000124d8e104b4a in glXCreateContextAttribsARB (dpy=0x124d533f0000,
>     config=0x124d7a0e7300, share_context=0x0, direct=1, attrib_list=0x7f7ffffbe300)
>     at create_context.c:78
> 
> Signed-off-by: Jonathan Gray <jsg at jsg.id.au>
> ---
>  src/mesa/main/debug_output.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/src/mesa/main/debug_output.c b/src/mesa/main/debug_output.c
> index 48dbbb3..bc933db 100644
> --- a/src/mesa/main/debug_output.c
> +++ b/src/mesa/main/debug_output.c
> @@ -1282,14 +1282,13 @@ _mesa_init_debug_output(struct gl_context *ctx)
>         */
>        struct gl_debug_state *debug = _mesa_lock_debug_state(ctx);
>        if (!debug) {
> -         goto done;
> +         return;
>        }
>        debug->DebugOutput = GL_TRUE;
>        debug->LogToStderr = GL_TRUE;
>        ctx->Const.ContextFlags |= GL_CONTEXT_FLAG_DEBUG_BIT;
> +      _mesa_unlock_debug_state(ctx);
>     }
> -done:
> -   _mesa_unlock_debug_state(ctx);
>  }
>  
>  
>