netdev - RE: [EXT] Re: [PATCH v3 net] qed/qede: Fix scheduling while atomic

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Date: Wed, 17 May 2023 20:10:11 +0000
From: Manish Chopra <manishc@...vell.com>
To: Jakub Kicinski <kuba@...nel.org>
CC: Stephen Hemminger <stephen@...workplumber.org>,
        "netdev@...r.kernel.org"
	<netdev@...r.kernel.org>,
        Ariel Elior <aelior@...vell.com>, Alok Prasad
	<palok@...vell.com>,
        Sudarsana Reddy Kalluru <skalluru@...vell.com>,
        "David S
 . Miller" <davem@...emloft.net>
Subject: RE: [EXT] Re: [PATCH v3 net] qed/qede: Fix scheduling while atomic

Hi Jakub,

> -----Original Message-----
> From: Jakub Kicinski <kuba@...nel.org>
> Sent: Wednesday, May 3, 2023 8:33 AM
> To: Manish Chopra <manishc@...vell.com>
> Cc: Stephen Hemminger <stephen@...workplumber.org>;
> netdev@...r.kernel.org; Ariel Elior <aelior@...vell.com>; Alok Prasad
> <palok@...vell.com>; Sudarsana Reddy Kalluru <skalluru@...vell.com>;
> David S . Miller <davem@...emloft.net>
> Subject: [EXT] Re: [PATCH v3 net] qed/qede: Fix scheduling while atomic
> 
> External Email
> 
> ----------------------------------------------------------------------
> On Fri, 28 Apr 2023 10:26:51 -0700 Stephen Hemminger wrote:
> > On Fri, 28 Apr 2023 09:13:37 -0700
> > Manish Chopra <manishc@...vell.com> wrote:
> >
> > > -		usleep_range(1000, 2000);
> > > +
> > > +		if (is_atomic)
> > > +			udelay(QED_BAR_ACQUIRE_TIMEOUT_UDELAY);
> > > +		else
> > > +			usleep_range(QED_BAR_ACQUIRE_TIMEOUT_USLEEP,
> > > +				     QED_BAR_ACQUIRE_TIMEOUT_USLEEP *
> 2);
> > >  	}
> >
> > This is a variant of the conditional locking which is an ugly design pattern.
> > It makes static checking tools break and a source of more bugs.
> >
> > Better to fix the infrastructure or caller to not spin, or have two
> > different functions.
> 
> FWIW the most common way to solve this issue is using a delayed work which
> reads out the stats periodically from a non-atomic context, and return a
> stashed copy from get_stat64.

Thanks for the suggestion, I will send v4 soon with required changes.

Regards,
Manish