Re: Linux v5.0-rc7: bcm2835 MMC issues

[Stefan Wahren <stefan.wahren-eS4NqCHxEME@public.gmane.org>]

> Aaro Koskinen <aaro.koskinen@iki.fi> hat am 29. März 2019 um 20:19 geschrieben:
> 
> 
> Hi,
> 
> On Fri, Mar 29, 2019 at 12:58:18AM +0200, Aaro Koskinen wrote:
> > On Sun, Mar 10, 2019 at 02:51:31AM +0200, Aaro Koskinen wrote:
> > > On Sat, Mar 09, 2019 at 11:57:57AM +0100, Stefan Wahren wrote:
> > > > > Aaro Koskinen <aaro.koskinen@iki.fi> hat am 27. Februar 2019 um 19:51 geschrieben:
> > > > > On Tue, Feb 26, 2019 at 09:31:14AM +0100, Stefan Wahren wrote:
> > > > > > it will take some time for to setup this test scenario. Could you please
> > > > > > do me a favor and test 4.20.12 which has some backports of recent mmc /
> > > > > > DMA fixes.
> > > > > 
> > > > > Both 4.20 and 4.20.12 work fine. Only 5.0-rc fails reliably.
> > > > 
> > > > I tried to reproduce the issue by compiling gcc and using stress on
> > > > Raspberry Pi 3 (arm64/defconfig) with Arch Linux ARM without any luck.
> > > > 
> > > > Were you able to reproduce the issue using stress?
> > > 
> > > No, not yet. I'll let you know if I'm able to come up with a more reliable
> > > reproducer.
> > 
> > I tried GCC bootstrap again with 5.1-rc2 and LOCKDEP enabled, and get
> > the below warning. Might some different unrelated issue, however.
> 
> So with 5.1-rc2, the GCC bootstrap & testsuite went fine (some 20 hours)
> without any MMC timeout errors or lockups. Also I think the below may
> be the cause of the earlier problems I had:
> 
> > [ 1164.390902] 
> > [ 1164.398302] ======================================================
> > [ 1164.416501] WARNING: possible circular locking dependency detected
> > [ 1164.434710] 5.1.0-rc2-rpi3-los_6ba38c+-00247-g9936328b41ce-dirty #1 Not tainted
> > [ 1164.454495] ------------------------------------------------------
> > [ 1164.472908] cc1plus/30873 is trying to acquire lock:
> > [ 1164.489750] 0000000040a8ff57 (&mq->complete_lock){+.+.}, at: mmc_blk_mq_complete_prev_req.part.12+0x3c/0x220
> > [ 1164.518548] 
> > [ 1164.518548] but task is already holding lock:
> > [ 1164.541662] 0000000059d7e9bb (fs_reclaim){+.+.}, at: fs_reclaim_acquire.part.19+0x0/0x40
> > [ 1164.567105] 
> > [ 1164.567105] which lock already depends on the new lock.
> > [ 1164.567105] 
> > [ 1164.595691] 
> > [ 1164.595691] the existing dependency chain (in reverse order) is:
> > [ 1164.616711] 
> > [ 1164.616711] -> #2 (fs_reclaim){+.+.}:
> > [ 1164.630507]        lock_acquire+0xe8/0x250
> > [ 1164.638922]        fs_reclaim_acquire.part.19+0x34/0x40
> > [ 1164.652170]        fs_reclaim_acquire+0x20/0x28
> > [ 1164.665139]        __kmalloc+0x50/0x390
> > [ 1164.673717]        bcm2835_dma_create_cb_chain+0x70/0x270
>                                  
> I think the bug is that it's using GFP_KERNEL here.

Hm, i'm not sure about how to solve this properly. Can you try this, because i wasn't able to reproduce this:

diff --git a/drivers/dma/bcm2835-dma.c b/drivers/dma/bcm2835-dma.c
index ec8a291..54093ff 100644
--- a/drivers/dma/bcm2835-dma.c
+++ b/drivers/dma/bcm2835-dma.c
@@ -671,7 +671,7 @@ static struct dma_async_tx_descriptor *bcm2835_dma_prep_slave_sg(
        d = bcm2835_dma_create_cb_chain(chan, direction, false,
                                        info, extra,
                                        frames, src, dst, 0, 0,
-                                       GFP_KERNEL);
+                                       GFP_NOWAIT);
        if (!d)
                return NULL;

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