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From: Alex Elder <elder@linaro.org>
To: Jakub Kicinski <kuba@kernel.org>
Cc: davem@davemloft.net, bjorn.andersson@linaro.org,
	evgreen@chromium.org, cpratapa@codeaurora.org,
	subashab@codeaurora.org, elder@kernel.org,
	netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH net-next 4/6] net: ipa: ensure hardware has power in ipa_start_xmit()
Date: Mon, 16 Aug 2021 09:20:40 -0500	[thread overview]
Message-ID: <b6b1ca41-36de-bcb1-30ca-6e8d8bfcc5a9@linaro.org> (raw)
In-Reply-To: <20210816071543.39a44815@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>

On 8/16/21 9:15 AM, Jakub Kicinski wrote:
> On Fri, 13 Aug 2021 21:25:23 -0500 Alex Elder wrote:
>>> This is racy, what if the pm work gets scheduled on another CPU and
>>> calls wake right here (i.e. before you call netif_stop_queue())?
>>> The queue may never get woken up?
>>
>> I haven't been seeing this happen but I think you may be right.
>>
>> I did think about this race, but I think I was relying on the
>> PM work queue to somehow avoid the problem.  I need to think
>> about this again after a good night's sleep.  I might need
>> to add an atomic flag or something.
> 
> Maybe add a spin lock?  Seems like the whole wake up path will be
> expensive enough for a spin lock to be in the noise. You can always
> add complexity later.

Exactly what I just decided after trying to work out a
clever way without using a spinlock...  I'll be sending
out a fix today.  Thanks.

					-Alex


  reply	other threads:[~2021-08-16 14:20 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-12 19:50 [PATCH net-next 0/6] net: ipa: last things before PM conversion Alex Elder
2021-08-12 19:50 ` [PATCH net-next 1/6] net: ipa: enable wakeup in ipa_power_setup() Alex Elder
2021-08-12 19:50 ` [PATCH net-next 2/6] net: ipa: distinguish system from runtime suspend Alex Elder
2021-08-12 19:50 ` [PATCH net-next 3/6] net: ipa: re-enable transmit in PM WQ context Alex Elder
2021-08-14  0:44   ` Jakub Kicinski
2021-08-14  2:32     ` Alex Elder
2021-08-12 19:50 ` [PATCH net-next 4/6] net: ipa: ensure hardware has power in ipa_start_xmit() Alex Elder
2021-08-14  0:46   ` Jakub Kicinski
2021-08-14  2:25     ` Alex Elder
2021-08-16 14:15       ` Jakub Kicinski
2021-08-16 14:20         ` Alex Elder [this message]
2021-08-16 17:56           ` Alex Elder
2021-08-16 20:19             ` Jakub Kicinski
2021-08-12 19:50 ` [PATCH net-next 5/6] net: ipa: don't stop TX on suspend Alex Elder
2021-08-12 19:50 ` [PATCH net-next 6/6] net: ipa: don't hold clock reference while netdev open Alex Elder
2021-08-14 13:20 ` [PATCH net-next 0/6] net: ipa: last things before PM conversion patchwork-bot+netdevbpf

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