linux-kernel - Re: [PATCH v5 3/4] mtd: core: protect access to MTD devices while in suspend

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Message-ID: <20211203143958.40645506@xps13>
Date:   Fri, 3 Dec 2021 14:39:58 +0100
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Boris Brezillon <boris.brezillon@...labora.com>
Cc:     Sean Nyekjaer <sean@...nix.com>, linux-kernel@...r.kernel.org,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        Boris Brezillon <bbrezillon@...nel.org>,
        linux-mtd@...ts.infradead.org
Subject: Re: [PATCH v5 3/4] mtd: core: protect access to MTD devices while
 in suspend

Hello,

> > Fine by me, lets drop this series.

FYI I've dropped the entire series from mtd/next. I'm waiting for the
fix discussed below (without abusing the chip mutex ;-) ).

Cheers,
Miquèl

> > We have +10.000 devices that runs with this patch:
> > 
> > diff --git a/drivers/mtd/nand/raw/nand_base.c b/drivers/mtd/nand/raw/nand_base.c
> > index 1f0d542d5923..58d48c3070fa 100644
> > --- a/drivers/mtd/nand/raw/nand_base.c
> > +++ b/drivers/mtd/nand/raw/nand_base.c
> > @@ -4337,7 +4337,6 @@ static int nand_suspend(struct mtd_info *mtd)
> >  		ret = chip->ops.suspend(chip);
> >  	if (!ret)
> >  		chip->suspended = 1;
> > -	mutex_unlock(&chip->lock);
> >  
> >  	return ret;
> >  }
> > @@ -4350,7 +4349,6 @@ static void nand_resume(struct mtd_info *mtd)
> >  {
> >  	struct nand_chip *chip = mtd_to_nand(mtd);
> >  
> > -	mutex_lock(&chip->lock);
> >  	if (chip->suspended) {
> >  		if (chip->ops.resume)
> >  			chip->ops.resume(chip);
> >   
> 
> But it's abusing the chip lock... Use a wait queue as we did at the MTD
> level, and make nand_get_device() wait on this wait queue when the
> device is suspended.
> 
> ______________________________________________________
> Linux MTD discussion mailing list
> http://lists.infradead.org/mailman/listinfo/linux-mtd/

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