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[91.14.161.181]) by smtp.gmail.com with ESMTPSA id l124sm19159561wml.8.2021.09.20.03.14.42 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 20 Sep 2021 03:14:42 -0700 (PDT) Subject: Re: [Intel-gfx] [PATCH 14/26] drm/i915: use the new iterator in i915_sw_fence_await_reservation v3 To: Tvrtko Ursulin , linaro-mm-sig@lists.linaro.org, dri-devel@lists.freedesktop.org, linux-media@vger.kernel.org, intel-gfx@lists.freedesktop.org Cc: daniel@ffwll.ch References: <20210917123513.1106-1-christian.koenig@amd.com> <20210917123513.1106-15-christian.koenig@amd.com> <93b93f00-7ad3-9ea3-e947-77297b4552c9@linux.intel.com> <60595ff8-7935-c0a4-7c0f-2a4c3a1d62b9@linux.intel.com> From: =?UTF-8?Q?Christian_K=c3=b6nig?= Message-ID: <3a029992-a648-7684-235e-b5bc53391d5d@gmail.com> Date: Mon, 20 Sep 2021 12:14:41 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 MIME-Version: 1.0 In-Reply-To: <60595ff8-7935-c0a4-7c0f-2a4c3a1d62b9@linux.intel.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org Am 20.09.21 um 10:47 schrieb Tvrtko Ursulin: > > On 20/09/2021 09:45, Tvrtko Ursulin wrote: >> >> On 17/09/2021 13:35, Christian König wrote: >>> Simplifying the code a bit. >>> >>> v2: use dma_resv_for_each_fence instead, according to Tvrtko the >>> lock is >>>      held here anyway. >>> v3: back to using dma_resv_for_each_fence_unlocked. >> >> It did not work out - what happened? > Wait, my suggestion to try the locked iterator was against > i915_request_await_object. I haven't looked at this one at the time or > even now. Exactly! I've mixed the two up and this one here is really called without holding a lock. Regards, Christian. > > Regards, > > Tvrtko > > >> Regards, >> >> Tvrtko >> >>> Signed-off-by: Christian König >>> --- >>>   drivers/gpu/drm/i915/i915_sw_fence.c | 57 >>> ++++++++-------------------- >>>   1 file changed, 15 insertions(+), 42 deletions(-) >>> >>> diff --git a/drivers/gpu/drm/i915/i915_sw_fence.c >>> b/drivers/gpu/drm/i915/i915_sw_fence.c >>> index c589a681da77..7635b0478ea5 100644 >>> --- a/drivers/gpu/drm/i915/i915_sw_fence.c >>> +++ b/drivers/gpu/drm/i915/i915_sw_fence.c >>> @@ -572,56 +572,29 @@ int i915_sw_fence_await_reservation(struct >>> i915_sw_fence *fence, >>>                       unsigned long timeout, >>>                       gfp_t gfp) >>>   { >>> -    struct dma_fence *excl; >>> +    struct dma_resv_iter cursor; >>> +    struct dma_fence *f; >>>       int ret = 0, pending; >>>       debug_fence_assert(fence); >>>       might_sleep_if(gfpflags_allow_blocking(gfp)); >>> -    if (write) { >>> -        struct dma_fence **shared; >>> -        unsigned int count, i; >>> - >>> -        ret = dma_resv_get_fences(resv, &excl, &count, &shared); >>> -        if (ret) >>> -            return ret; >>> - >>> -        for (i = 0; i < count; i++) { >>> -            if (shared[i]->ops == exclude) >>> -                continue; >>> - >>> -            pending = i915_sw_fence_await_dma_fence(fence, >>> -                                shared[i], >>> -                                timeout, >>> -                                gfp); >>> -            if (pending < 0) { >>> -                ret = pending; >>> -                break; >>> -            } >>> - >>> -            ret |= pending; >>> -        } >>> - >>> -        for (i = 0; i < count; i++) >>> -            dma_fence_put(shared[i]); >>> -        kfree(shared); >>> -    } else { >>> -        excl = dma_resv_get_excl_unlocked(resv); >>> -    } >>> - >>> -    if (ret >= 0 && excl && excl->ops != exclude) { >>> -        pending = i915_sw_fence_await_dma_fence(fence, >>> -                            excl, >>> -                            timeout, >>> +    rcu_read_lock(); >>> +    dma_resv_iter_begin(&cursor, resv, write); >>> +    dma_resv_for_each_fence_unlocked(&cursor, f) { >>> +        rcu_read_unlock(); >>> +        pending = i915_sw_fence_await_dma_fence(fence, f, timeout, >>>                               gfp); >>> -        if (pending < 0) >>> +        rcu_read_lock(); >>> +        if (pending < 0) { >>>               ret = pending; >>> -        else >>> -            ret |= pending; >>> -    } >>> - >>> -    dma_fence_put(excl); >>> +            break; >>> +        } >>> +        ret |= pending; >>> +    } >>> +    dma_resv_iter_end(&cursor); >>> +    rcu_read_unlock(); >>>       return ret; >>>   } >>>