From: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
To: Chris Wilson <chris@chris-wilson.co.uk>, intel-gfx@lists.freedesktop.org
Subject: Re: [PATCH igt] igt/gem_exec_await: Flush the WCB before attempting to queue more work
Date: Fri, 22 Dec 2017 17:03:46 +0000 [thread overview]
Message-ID: <bde4e166-7f90-40ea-4345-2b35a5a3d136@linux.intel.com> (raw)
In-Reply-To: <20171221154823.23766-1-chris@chris-wilson.co.uk>
On 21/12/2017 15:48, Chris Wilson wrote:
> Ensure that the terminating write into WC-memory is flushed before we
> might trigger a wait for ring space.
>
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> ---
> tests/gem_exec_await.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/tests/gem_exec_await.c b/tests/gem_exec_await.c
> index 9c4467922..28b280ff6 100644
> --- a/tests/gem_exec_await.c
> +++ b/tests/gem_exec_await.c
> @@ -222,6 +222,7 @@ static void wide(int fd, int ring_size, int timeout, unsigned int flags)
>
> for (unsigned e = 0; e < nengine; e++)
> exec[e].cmd[0] = MI_BATCH_BUFFER_END;
> + __sync_synchronize();
> }
>
> igt_assert_eq(intel_detect_and_clear_missed_interrupts(fd), 0);
>
In case someone is reading from the same uneducated situation as I was,
__sync_synchronize emits an mfence instructions which indeed forces a
flush of the write combine buffer.
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Regards,
Tvrtko
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prev parent reply other threads:[~2017-12-22 17:03 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-12-21 15:48 [PATCH igt] igt/gem_exec_await: Flush the WCB before attempting to queue more work Chris Wilson
2017-12-21 16:05 ` ✓ Fi.CI.BAT: success for " Patchwork
2017-12-21 16:56 ` ✗ Fi.CI.IGT: warning " Patchwork
2017-12-22 17:03 ` Tvrtko Ursulin [this message]
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