From: Robert Jarzmik <robert.jarzmik@free.fr> To: Petr Cvek <petr.cvek@tul.cz> Cc: ulf.hansson@linaro.org, linux-mmc@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH 4/4] mmc: pxamci: Fix race condition between pxamci_dma_irq() and pxamci_irq() Date: Thu, 27 Apr 2017 15:14:28 +0200 [thread overview] Message-ID: <87inlq0z7v.fsf@belgarion.home> (raw) In-Reply-To: <43c3a3b4-75b5-613e-4e28-9c38271ccb63@tul.cz> (Petr Cvek's message of "Fri, 21 Apr 2017 03:30:10 +0200") Petr Cvek <petr.cvek@tul.cz> writes: > Dne 19.4.2017 v 21:22 Robert Jarzmik napsal(a): >> Petr Cvek <petr.cvek@tul.cz> writes: Hi Petr, As promised, I though it a bit more, and I have a counter proposal, which looks simpler (if it works for you). Why not remove completely the call to pxamci_data_done() from pxamci_dma_irq() ? The pxamci_dma_irq() will only remain for the partial full write, and for the dev_err() part, but won't act on command completion, that part being full dealt with by pxamci_data_done(). I still seeing a small race window, in that : - DATA_TRAN_DONE is asserted for a MMC read transaction, because the MMC FIFO was just emptied by the DMA IP - imagine the memory is not yet written to by the DMA IP (ie. this is the race window, the DATA being help in DMA IP internal FIFO) - the pxamci_data_done() is called, and it calls dma_unmap_sg(), flushing the cache - the consumer reads this last data bit, which is still the old data, and then the DMA finishes ... I know the probability is almost 0 for this scenario to happen given the timings, it's just to add fuel to the technical exchange. > The patches 1, 1+2, 1+2+3 should boot, but the MMC will of course fail as only > the 4 repairs it. Do you want me to send them independently? (or I can sort > them that the race condition repair is the first one) No no, I like it the way it is, and as far as Ulf is happy as his tree will carry them, I'm happy too. Cheers. -- Robert
WARNING: multiple messages have this Message-ID (diff)
From: robert.jarzmik@free.fr (Robert Jarzmik) To: linux-arm-kernel@lists.infradead.org Subject: [PATCH 4/4] mmc: pxamci: Fix race condition between pxamci_dma_irq() and pxamci_irq() Date: Thu, 27 Apr 2017 15:14:28 +0200 [thread overview] Message-ID: <87inlq0z7v.fsf@belgarion.home> (raw) In-Reply-To: <43c3a3b4-75b5-613e-4e28-9c38271ccb63@tul.cz> (Petr Cvek's message of "Fri, 21 Apr 2017 03:30:10 +0200") Petr Cvek <petr.cvek@tul.cz> writes: > Dne 19.4.2017 v 21:22 Robert Jarzmik napsal(a): >> Petr Cvek <petr.cvek@tul.cz> writes: Hi Petr, As promised, I though it a bit more, and I have a counter proposal, which looks simpler (if it works for you). Why not remove completely the call to pxamci_data_done() from pxamci_dma_irq() ? The pxamci_dma_irq() will only remain for the partial full write, and for the dev_err() part, but won't act on command completion, that part being full dealt with by pxamci_data_done(). I still seeing a small race window, in that : - DATA_TRAN_DONE is asserted for a MMC read transaction, because the MMC FIFO was just emptied by the DMA IP - imagine the memory is not yet written to by the DMA IP (ie. this is the race window, the DATA being help in DMA IP internal FIFO) - the pxamci_data_done() is called, and it calls dma_unmap_sg(), flushing the cache - the consumer reads this last data bit, which is still the old data, and then the DMA finishes ... I know the probability is almost 0 for this scenario to happen given the timings, it's just to add fuel to the technical exchange. > The patches 1, 1+2, 1+2+3 should boot, but the MMC will of course fail as only > the 4 repairs it. Do you want me to send them independently? (or I can sort > them that the race condition repair is the first one) No no, I like it the way it is, and as far as Ulf is happy as his tree will carry them, I'm happy too. Cheers. -- Robert
next prev parent reply other threads:[~2017-04-27 13:14 UTC|newest] Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top [not found] <cover.1492492523.git.petr.cvek@tul.cz> 2017-04-18 23:16 ` [PATCH 1/4] mmc: pxamci: Use the right flags for DMA callback init Petr Cvek 2017-04-18 23:16 ` Petr Cvek 2017-04-21 0:31 ` Petr Cvek 2017-04-21 0:31 ` Petr Cvek 2017-04-18 23:17 ` [PATCH 2/4] mmc: pxamci: Enhance error checking Petr Cvek 2017-04-18 23:17 ` Petr Cvek 2017-04-19 19:12 ` Robert Jarzmik 2017-04-19 19:12 ` Robert Jarzmik 2017-04-18 23:17 ` [PATCH 3/4] mmc: pxamci: Disable DATA_TRAN_DONE interrupt sooner Petr Cvek 2017-04-18 23:17 ` Petr Cvek 2017-04-19 19:14 ` Robert Jarzmik 2017-04-19 19:14 ` Robert Jarzmik 2017-04-20 23:37 ` Petr Cvek 2017-04-20 23:37 ` Petr Cvek 2017-04-18 23:18 ` [PATCH 4/4] mmc: pxamci: Fix race condition between pxamci_dma_irq() and pxamci_irq() Petr Cvek 2017-04-18 23:18 ` Petr Cvek 2017-04-19 19:22 ` Robert Jarzmik 2017-04-19 19:22 ` Robert Jarzmik 2017-04-21 1:30 ` Petr Cvek 2017-04-21 1:30 ` Petr Cvek 2017-04-27 13:14 ` Robert Jarzmik [this message] 2017-04-27 13:14 ` Robert Jarzmik
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