From: "Marek Behún" <kabel@kernel.org>
To: Ben Whitten <ben.whitten@gmail.com>
Cc: linux-leds@vger.kernel.org
Subject: ledtrig netdev: what is the purpose of spinlock usage?
Date: Thu, 29 Oct 2020 07:00:00 +0100 [thread overview]
Message-ID: <20201029070000.15472666@kernel.org> (raw)
Hi Ben (or Pavel or whomever can explain this),
since you are the original author of netdev LED trigger, I guess this
question should go to you. Why are spinlocks used as locks in the
netdev trigger code? Is this for performance? Would it be a drastic
performance hit to use mutexes?
The reason why I am asking is that I am designing an API for transparent
HW offload of LED triggers. (Some LEDs, eg. LEDs on ethernet PHYs, can
blink on rx/tx activity themselves).
You can find this at
https://git.kernel.org/pub/scm/linux/kernel/git/kabel/linux.git/log/?h=leds-trigger-hw-offload
The current approach for the netdev trigger is that the
set_baseline_state function calls trigger_offload() method of the LED
classdev. But the whole set_baseline_state function is called from
within spinlock, and so when the trigger_offload method calls something
that can sleep (MDIO bus communication, for example), kernel complains:
BUG: scheduling while atomic
Thanks.
Marek
next reply other threads:[~2020-10-29 8:27 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-29 6:00 Marek Behún [this message]
2020-10-29 17:45 ` ledtrig netdev: what is the purpose of spinlock usage? Pavel Machek
2020-10-29 18:13 ` Marek Behún
2020-10-29 21:32 ` Ben Whitten
2020-10-29 22:49 ` Jacek Anaszewski
2020-10-29 23:14 ` Marek Behún
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