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From: "Rakesh Pillai" <pillair@codeaurora.org>
To: "'Johannes Berg'" <johannes@sipsolutions.net>,
	<ath10k@lists.infradead.org>
Cc: <linux-wireless@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
	<kvalo@codeaurora.org>, <davem@davemloft.net>, <kuba@kernel.org>,
	<netdev@vger.kernel.org>, <dianders@chromium.org>,
	<evgreen@chromium.org>
Subject: RE: [RFC 1/7] mac80211: Add check for napi handle before WARN_ON
Date: Fri, 24 Jul 2020 11:51:12 +0530	[thread overview]
Message-ID: <000401d66182$a3d97ab0$eb8c7010$@codeaurora.org> (raw)
In-Reply-To: <ce380ea1fd1f5db40a92f67673f070a1f88eee50.camel@sipsolutions.net>



> -----Original Message-----
> From: Johannes Berg <johannes@sipsolutions.net>
> Sent: Friday, July 24, 2020 1:37 AM
> To: Rakesh Pillai <pillair@codeaurora.org>; ath10k@lists.infradead.org
> Cc: linux-wireless@vger.kernel.org; linux-kernel@vger.kernel.org;
> kvalo@codeaurora.org; davem@davemloft.net; kuba@kernel.org;
> netdev@vger.kernel.org; dianders@chromium.org; evgreen@chromium.org
> Subject: Re: [RFC 1/7] mac80211: Add check for napi handle before
> WARN_ON
> 
> On Thu, 2020-07-23 at 23:56 +0530, Rakesh Pillai wrote:
> 
> > > > -	WARN_ON_ONCE(softirq_count() == 0);
> > > > +	WARN_ON_ONCE(napi && softirq_count() == 0);
> > >
> > > FWIW, I'm pretty sure this is incorrect - we make assumptions on
> > > softirqs being disabled in mac80211 for serialization and in place of
> > > some locking, I believe.
> > >
> >
> > I checked this, but let me double confirm.
> > But after this change, no packet is submitted from driver in a softirq
> context.
> > So ideally this should take care of serialization.
> 
> I'd guess that we have some reliance on BHs already being disabled, for
> things like u64 sync updates, or whatnot. I mean, we did "rx_ni()" for a
> reason ... Maybe lockdep can help catch some of the issues.
> 
> But couldn't you be in a thread and have BHs disabled too?

This would ideally beat the purpose and possibly hurt the other subsystems running on the same core.

> 
> johannes



WARNING: multiple messages have this Message-ID

From: "Rakesh Pillai" <pillair@codeaurora.org>
To: 'Johannes Berg' <johannes@sipsolutions.net>, ath10k@lists.infradead.org
Cc: netdev@vger.kernel.org, linux-wireless@vger.kernel.org,
	linux-kernel@vger.kernel.org, evgreen@chromium.org,
	dianders@chromium.org, kuba@kernel.org, davem@davemloft.net,
	kvalo@codeaurora.org
Subject: RE: [RFC 1/7] mac80211: Add check for napi handle before WARN_ON
Date: Fri, 24 Jul 2020 11:51:12 +0530	[thread overview]
Message-ID: <000401d66182$a3d97ab0$eb8c7010$@codeaurora.org> (raw)
In-Reply-To: <ce380ea1fd1f5db40a92f67673f070a1f88eee50.camel@sipsolutions.net>



> -----Original Message-----
> From: Johannes Berg <johannes@sipsolutions.net>
> Sent: Friday, July 24, 2020 1:37 AM
> To: Rakesh Pillai <pillair@codeaurora.org>; ath10k@lists.infradead.org
> Cc: linux-wireless@vger.kernel.org; linux-kernel@vger.kernel.org;
> kvalo@codeaurora.org; davem@davemloft.net; kuba@kernel.org;
> netdev@vger.kernel.org; dianders@chromium.org; evgreen@chromium.org
> Subject: Re: [RFC 1/7] mac80211: Add check for napi handle before
> WARN_ON
> 
> On Thu, 2020-07-23 at 23:56 +0530, Rakesh Pillai wrote:
> 
> > > > -	WARN_ON_ONCE(softirq_count() == 0);
> > > > +	WARN_ON_ONCE(napi && softirq_count() == 0);
> > >
> > > FWIW, I'm pretty sure this is incorrect - we make assumptions on
> > > softirqs being disabled in mac80211 for serialization and in place of
> > > some locking, I believe.
> > >
> >
> > I checked this, but let me double confirm.
> > But after this change, no packet is submitted from driver in a softirq
> context.
> > So ideally this should take care of serialization.
> 
> I'd guess that we have some reliance on BHs already being disabled, for
> things like u64 sync updates, or whatnot. I mean, we did "rx_ni()" for a
> reason ... Maybe lockdep can help catch some of the issues.
> 
> But couldn't you be in a thread and have BHs disabled too?

This would ideally beat the purpose and possibly hurt the other subsystems running on the same core.

> 
> johannes



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  reply	other threads:[~2020-07-24  6:21 UTC|newest]

Thread overview: 96+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-21 17:14 [RFC 0/7] Add support to process rx packets in thread Rakesh Pillai
2020-07-21 17:14 ` Rakesh Pillai
2020-07-21 17:14 ` [RFC 1/7] mac80211: Add check for napi handle before WARN_ON Rakesh Pillai
2020-07-21 17:14   ` Rakesh Pillai
2020-07-22 12:56   ` Johannes Berg
2020-07-22 12:56     ` Johannes Berg
2020-07-23 18:26     ` Rakesh Pillai
2020-07-23 18:26       ` Rakesh Pillai
2020-07-23 20:06       ` Johannes Berg
2020-07-23 20:06         ` Johannes Berg
2020-07-24  6:21         ` Rakesh Pillai [this message]
2020-07-24  6:21           ` Rakesh Pillai
2020-07-26 16:19         ` Rakesh Pillai
2020-07-26 16:19           ` Rakesh Pillai
2020-07-30 12:40           ` Johannes Berg
2020-07-30 12:40             ` Johannes Berg
2020-07-21 17:14 ` [RFC 2/7] ath10k: Add support to process rx packet in thread Rakesh Pillai
2020-07-21 17:14   ` Rakesh Pillai
2020-07-21 21:53   ` Rajkumar Manoharan
2020-07-21 21:53     ` Rajkumar Manoharan
2020-07-22 12:27     ` Felix Fietkau
2020-07-22 12:27       ` Felix Fietkau
2020-07-22 12:55       ` Johannes Berg
2020-07-22 12:55         ` Johannes Berg
2020-07-22 13:00         ` Felix Fietkau
2020-07-22 13:00           ` Felix Fietkau
2020-07-23  6:09           ` Rajkumar Manoharan
2020-07-23  6:09             ` Rajkumar Manoharan
2021-03-22 23:57           ` Ben Greear
2021-03-22 23:57             ` Ben Greear
2021-03-23  1:20             ` Brian Norris
2021-03-23  1:20               ` Brian Norris
2021-03-23  3:01               ` Ben Greear
2021-03-23  3:01                 ` Ben Greear
2021-03-23  7:45                 ` Felix Fietkau
2021-03-23  7:45                   ` Felix Fietkau
2021-03-25  9:45                   ` Rakesh Pillai
2021-03-25  9:45                     ` Rakesh Pillai
2021-03-25 10:33                     ` Felix Fietkau
2021-03-25 10:33                       ` Felix Fietkau
2020-07-23 18:25     ` Rakesh Pillai
2020-07-23 18:25       ` Rakesh Pillai
2020-07-24 23:11       ` Jacob Keller
2020-07-24 23:11         ` Jacob Keller
2020-07-21 17:14 ` [RFC 3/7] ath10k: Add module param to enable rx thread Rakesh Pillai
2020-07-21 17:14   ` Rakesh Pillai
2020-07-21 17:14 ` [RFC 4/7] ath10k: Do not exhaust budget on process tx completion Rakesh Pillai
2020-07-21 17:14   ` Rakesh Pillai
2020-07-21 17:14 ` [RFC 5/7] ath10k: Handle the rx packet processing in thread Rakesh Pillai
2020-07-21 17:14   ` Rakesh Pillai
2020-07-21 17:14 ` [RFC 6/7] ath10k: Add deliver to stack from thread context Rakesh Pillai
2020-07-21 17:14   ` Rakesh Pillai
2020-07-21 17:14 ` [RFC 7/7] ath10k: Handle rx thread suspend and resume Rakesh Pillai
2020-07-21 17:14   ` Rakesh Pillai
2020-07-23 23:06   ` Sebastian Gottschall
2020-07-23 23:06     ` Sebastian Gottschall
2020-07-24  6:19     ` Rakesh Pillai
2020-07-24  6:19       ` Rakesh Pillai
2020-07-21 17:25 ` [RFC 0/7] Add support to process rx packets in thread Andrew Lunn
2020-07-21 17:25   ` Andrew Lunn
2020-07-21 18:05   ` Florian Fainelli
2020-07-21 18:05     ` Florian Fainelli
2020-07-23 18:21     ` Rakesh Pillai
2020-07-23 18:21       ` Rakesh Pillai
2020-07-23 19:02       ` Florian Fainelli
2020-07-23 19:02         ` Florian Fainelli
2020-07-24  6:20         ` Rakesh Pillai
2020-07-24  6:20           ` Rakesh Pillai
2020-07-24 22:28           ` Florian Fainelli
2020-07-24 22:28             ` Florian Fainelli
2020-07-22  9:12   ` David Laight
2020-07-22  9:12     ` David Laight
2020-07-25  8:16     ` Hillf Danton
2020-07-25 10:38       ` Sebastian Gottschall
2020-07-25 10:38         ` Sebastian Gottschall
2020-07-25 12:25         ` Hillf Danton
2020-07-25 14:08         ` Sebastian Gottschall
2020-07-25 14:08           ` Sebastian Gottschall
2020-07-25 14:57           ` Hillf Danton
2020-07-25 15:41             ` Sebastian Gottschall
2020-07-25 15:41               ` Sebastian Gottschall
2020-07-26 11:16               ` David Laight
2020-07-26 11:16                 ` David Laight
2020-07-28 16:59                 ` Rakesh Pillai
2020-07-28 16:59                   ` Rakesh Pillai
2020-07-29  1:34                   ` Hillf Danton
2020-07-25 17:57       ` Felix Fietkau
2020-07-25 17:57         ` Felix Fietkau
2020-07-26  1:22         ` Hillf Danton
2020-07-26  8:10           ` Felix Fietkau
2020-07-26  8:10             ` Felix Fietkau
2020-07-26  8:32             ` Hillf Danton
2020-07-26  8:59               ` Felix Fietkau
2020-07-26  8:59                 ` Felix Fietkau
2020-07-22 16:20   ` Jakub Kicinski
2020-07-22 16:20     ` Jakub Kicinski

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