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Sun, 15 Jun 2025 12:15:14 -0700 (PDT) Received: from gmail.com ([2a02:c7c:f4f0:900:5194:623a:df1:d4bc]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4532e13cfbesm118671195e9.22.2025.06.15.12.15.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 15 Jun 2025 12:15:12 -0700 (PDT) Date: Sun, 15 Jun 2025 20:15:07 +0100 From: Qasim Ijaz To: Sinan Kaya Cc: Eugen Hristev , Vinod Koul , linux-arm-kernel@lists.infradead.org, linux-arm-msm@vger.kernel.org, dmaengine@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH 2/2] dmaengine: qcom_hidma: fix handoff FIFO memory leak on driver removal Message-ID: References: <20250601224231.24317-1-qasdev00@gmail.com> <20250601224231.24317-3-qasdev00@gmail.com> <3c6513fe-83b3-4117-8df6-6f8c7eb07303@linaro.org> <7649f016-87f1-475d-8ff7-7608b14c5654@kernel.org> Precedence: bulk X-Mailing-List: dmaengine@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <7649f016-87f1-475d-8ff7-7608b14c5654@kernel.org> On Fri, Jun 06, 2025 at 09:35:44AM -0400, Sinan Kaya wrote: > > On 6/5/2025 9:04 AM, Eugen Hristev wrote: > > > diff --git a/drivers/dma/qcom/hidma_ll.c b/drivers/dma/qcom/hidma_ll.c > > > index fee448499777..0c2bae46746c 100644 > > > --- a/drivers/dma/qcom/hidma_ll.c > > > +++ b/drivers/dma/qcom/hidma_ll.c > > > @@ -816,6 +816,7 @@ int hidma_ll_uninit(struct hidma_lldev *lldev) > > > required_bytes = sizeof(struct hidma_tre) * lldev->nr_tres; > > > tasklet_kill(&lldev->task); > > > + kfifo_free(&lldev->handoff_fifo); > > > memset(lldev->trepool, 0, required_bytes); > > > lldev->trepool = NULL; > > > atomic_set(&lldev->pending_tre_count, 0); > > Is it possible that the handoff_fifo is freed, then we could observe > > reset complete interrupts before they are being cleared in > > hidma_ll_uninit later on, which would lead to the following call chain > > > > hidma_ll_inthandler - hidma_ll_int_handler_internal - > > hidma_handle_tre_completion - hidma_post_completed - > > tasklet_schedule(&lldev->task); - hidma_ll_tre_complete - kfifo_out > > According to the documentation, the way to guarantee this from not happening > > is to call tasklet_disable() to ensure that tasklet completes execution. > Only after that > > data structures used by the tasklet can be freed. > > I think proper order is: > > 1. tasklet_disable > > 2. tasklet_kill > > 3. kfifo_free Hi Sinan, hi Eugen, Thanks for reviewing the patch and for pointing out the correct shutdown ordering. If you’re both happy with it, I’ll send a v2 that calls tasklet_disable() before tasklet_kill(), then frees the handoff_fifo. Just let me know and I’ll resend. Thanks Qasim > > >