Messages in this thread Patch in this message | | | Date | Wed, 13 Jun 2012 20:43:05 +0530 | Subject | Re: [PATCH] DMA: PL330: Fix racy mutex unlock | From | Jassi Brar <> |
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On 13 June 2012 19:37, Javi Merino <javi.merino@arm.com> wrote: > pl330_update() stores a pointer to the thrd->req that finished, which > contains a pointer to the corresponding pl330_req. This is done with > the pl330_lock held. Then, it iterates through the req_done list, > calling the callback for each of the requests that are done. The > problem is that the driver releases the lock before calling the > callback for each of the callbacks. pl330_submit_req() running in > another processor can then acquire the lock and insert another request > in one of the thrd->req that hasn't been processed yet, replacing the > pointer to pl330_req there. When the callback returns in > pl330_update() and the next rqdone is popped from the list, it > dereferences the pl330_req pointer to the just scheduled pl330_req, > instead of the one that has finished, calling pl330 with the wrong r. > > This patch fixes this by storing the pointer to pl330_req directly in > the list. > ..... > @@ -1683,7 +1683,7 @@ static void pl330_dotask(unsigned long data) > /* Returns 1 if state was updated, 0 otherwise */ > static int pl330_update(const struct pl330_info *pi) > { > - struct _pl330_req *rqdone; > + struct pl330_req *rqdone, *tmp; > struct pl330_dmac *pl330; > unsigned long flags; > void __iomem *regs; > @@ -1750,7 +1750,10 @@ static int pl330_update(const struct pl330_info *pi) > if (active == -1) /* Aborted */ > continue; > > - rqdone = &thrd->req[active]; > + /* Detach the req */ > + rqdone = thrd->req[active].r; > + thrd->req[active].r = NULL; > + Doesn't this movement of "Detach the req" chunk effectively remain the same? Since that was already protected by the same lock. I thought I deliberately took care of that already.
Do you see some real problem fixed by this patch? Info about that could help me better understand if I missed something here.
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