[Mesa-dev] [PATCH v3 1/1] clover: Wait for requested operation if blocking flag is set

[Francisco Jerez]

Jan Vesely <jan.vesely at rutgers.edu> writes:

> On Fri, 2017-08-18 at 14:19 -0700, Francisco Jerez wrote:
>> Jan Vesely <jan.vesely at rutgers.edu> writes:
>> 
>> > v2: wait in map_buffer and map_image as well
>> > v3: use event::wait instead of wait (skips fence wait for hard_event)
>> > 
>> 
>> Unfortunately this won't wait for the event action to be executed, only
>> for all dependencies of the event to become signalled, so there's a
>> possibility for a race condition in a multi-threaded environment.  Using
>> wait_signalled as I suggested earlier would address this issue.
>
> There's no wait_signalled() function.

It's in the patch I sent to you in the mail where I suggested doing
that.

> event::signalled() returns !wait_count.
>
> event::wait()
> {
> --- This should wait for dependencies
>    for (event &ev : deps)
>       ev.wait();
>
> --- This should wait for signalled, no? at least the condition is
> identical

wait_count == deps.size() during most of the lifespan of a hard_event,
so the code below may return immediately even if the action hasn't been
executed yet (e.g. in a different thread).

>    std::unique_lock<std::mutex> lock(mutex);
>    cv.wait(lock, [=]{ return !wait_count; });
> }
> am I missing something?
>
> Jan
>
>> 
>> > Signed-off-by: Jan Vesely <jan.vesely at rutgers.edu>
>> > ---
>> >  src/gallium/state_trackers/clover/api/transfer.cpp | 30 ++++++++++++++++++++--
>> >  1 file changed, 28 insertions(+), 2 deletions(-)
>> > 
>> > diff --git a/src/gallium/state_trackers/clover/api/transfer.cpp b/src/gallium/state_trackers/clover/api/transfer.cpp
>> > index f7046253be..6f1ac4b931 100644
>> > --- a/src/gallium/state_trackers/clover/api/transfer.cpp
>> > +++ b/src/gallium/state_trackers/clover/api/transfer.cpp
>> > @@ -295,6 +295,9 @@ clEnqueueReadBuffer(cl_command_queue d_q, cl_mem d_mem, cl_bool blocking,
>> >                     &mem, obj_origin, obj_pitch,
>> >                     region));
>> >  
>> > +   if (blocking)
>> > +       hev().event::wait();
>> > +
>> >     ret_object(rd_ev, hev);
>> >     return CL_SUCCESS;
>> >  
>> > @@ -325,6 +328,9 @@ clEnqueueWriteBuffer(cl_command_queue d_q, cl_mem d_mem, cl_bool blocking,
>> >                     ptr, {}, obj_pitch,
>> >                     region));
>> >  
>> > +   if (blocking)
>> > +       hev().event::wait();
>> > +
>> >     ret_object(rd_ev, hev);
>> >     return CL_SUCCESS;
>> >  
>> > @@ -362,6 +368,9 @@ clEnqueueReadBufferRect(cl_command_queue d_q, cl_mem d_mem, cl_bool blocking,
>> >                     &mem, obj_origin, obj_pitch,
>> >                     region));
>> >  
>> > +   if (blocking)
>> > +       hev().event::wait();
>> > +
>> >     ret_object(rd_ev, hev);
>> >     return CL_SUCCESS;
>> >  
>> > @@ -399,6 +408,9 @@ clEnqueueWriteBufferRect(cl_command_queue d_q, cl_mem d_mem, cl_bool blocking,
>> >                     ptr, host_origin, host_pitch,
>> >                     region));
>> >  
>> > +   if (blocking)
>> > +       hev().event::wait();
>> > +
>> >     ret_object(rd_ev, hev);
>> >     return CL_SUCCESS;
>> >  
>> > @@ -504,6 +516,9 @@ clEnqueueReadImage(cl_command_queue d_q, cl_mem d_mem, cl_bool blocking,
>> >                     &img, src_origin, src_pitch,
>> >                     region));
>> >  
>> > +   if (blocking)
>> > +       hev().event::wait();
>> > +
>> >     ret_object(rd_ev, hev);
>> >     return CL_SUCCESS;
>> >  
>> > @@ -538,6 +553,9 @@ clEnqueueWriteImage(cl_command_queue d_q, cl_mem d_mem, cl_bool blocking,
>> >                     ptr, {}, src_pitch,
>> >                     region));
>> >  
>> > +   if (blocking)
>> > +       hev().event::wait();
>> > +
>> >     ret_object(rd_ev, hev);
>> >     return CL_SUCCESS;
>> >  
>> > @@ -667,7 +685,11 @@ clEnqueueMapBuffer(cl_command_queue d_q, cl_mem d_mem, cl_bool blocking,
>> >  
>> >     void *map = mem.resource(q).add_map(q, flags, blocking, obj_origin, region);
>> >  
>> > -   ret_object(rd_ev, create<hard_event>(q, CL_COMMAND_MAP_BUFFER, deps));
>> > +   auto hev = create<hard_event>(q, CL_COMMAND_MAP_BUFFER, deps);
>> > +   if (blocking)
>> > +       hev().event::wait();
>> > +
>> > +   ret_object(rd_ev, hev);
>> >     ret_error(r_errcode, CL_SUCCESS);
>> >     return map;
>> >  
>> > @@ -695,7 +717,11 @@ clEnqueueMapImage(cl_command_queue d_q, cl_mem d_mem, cl_bool blocking,
>> >  
>> >     void *map = img.resource(q).add_map(q, flags, blocking, origin, region);
>> >  
>> > -   ret_object(rd_ev, create<hard_event>(q, CL_COMMAND_MAP_IMAGE, deps));
>> > +   auto hev = create<hard_event>(q, CL_COMMAND_MAP_IMAGE, deps);
>> > +   if (blocking)
>> > +       hev().event::wait();
>> > +
>> > +   ret_object(rd_ev, hev);
>> >     ret_error(r_errcode, CL_SUCCESS);
>> >     return map;
>> >  
>> > -- 
>> > 2.13.5
>> 
>> _______________________________________________
>> mesa-dev mailing list
>> mesa-dev at lists.freedesktop.org
>> https://lists.freedesktop.org/mailman/listinfo/mesa-dev
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