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dmaengine: rcar-dmac: wait for ISR to finish before freeing resources

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This fixes a race condition where the channel resources could be freed
before the ISR had finished running resulting in a NULL pointer
reference from the ISR.

[  167.148934] Unable to handle kernel NULL pointer dereference at virtual address 00000000
[  167.157051] pgd = ffff80003c641000
[  167.160449] [00000000] *pgd=000000007c507003, *pud=000000007c4ff003, *pmd=0000000000000000
[  167.168719] Internal error: Oops: 96000046 [#1] PREEMPT SMP
[  167.174289] Modules linked in:
[  167.177348] CPU: 3 PID: 10547 Comm: dma_ioctl Not tainted 4.11.0-rc1-00001-g8d92afddc2f6633a #73
[  167.186131] Hardware name: Renesas Salvator-X board based on r8a7795 (DT)
[  167.192917] task: ffff80003a411a00 task.stack: ffff80003bcd4000
[  167.198850] PC is at rcar_dmac_chan_prep_sg+0xe0/0x400
[  167.203985] LR is at rcar_dmac_chan_prep_sg+0x48/0x400

Based of previous work by:
    Hiroyuki Yokoyama <hiroyuki.yokoyama.vx@renesas.com>.

Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
This commit is contained in:
Niklas Söderlund 2017-05-16 01:09:17 +02:00 committed by Vinod Koul
parent 30c45005a4
commit a1ed64efc5
1 changed files with 5 additions and 1 deletions
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6
drivers/dma/sh/rcar-dmac.c
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@ -1010,7 +1010,11 @@ static void rcar_dmac_free_chan_resources(struct dma_chan *chan)
rcar_dmac_chan_halt(rchan);
spin_unlock_irq(&rchan->lock);
/* Now no new interrupts will occur */
/*
* Now no new interrupts will occur, but one might already be
* running. Wait for it to finish before freeing resources.
*/
synchronize_irq(rchan->irq);
if (rchan->mid_rid >= 0) {
/* The caller is holding dma_list_mutex */