linux-kernel - Re: [PATCH] printk: Update @console_may_schedule in console_trylock

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Message-ID: <8734tfml8v.fsf@jogness.linutronix.de>
Date: Mon, 26 Feb 2024 14:08:40 +0106
From: John Ogness <john.ogness@...utronix.de>
To: Mukesh Ojha <quic_mojha@...cinc.com>, pmladek@...e.com,
 rostedt@...dmis.org, senozhatsky@...omium.org
Cc: linux-kernel@...r.kernel.org
Subject: Re: [PATCH] printk: Update @console_may_schedule in
 console_trylock_spinning()

On 2024-02-26, Mukesh Ojha <quic_mojha@...cinc.com> wrote:
> what if console_trylock_spinning() gets the lock which makes 
> console_may_schedule =1 and it is still schedulable ?

I am afraid I do not understand the question.

console_trylock_spinning() is only called from the printk caller
context. In this context, console_may_schedule is always set to 0.

Only if another context acquires the console lock per sleeping wait,
console_lock(), can console_may_schedule be set to 1.

Note that the value of console_may_schedule is only relevant for the
console lock owner when console_unlock() is called. That is why its
value is set when locking the console (or, with this patch, when
transferring console lock ownerhip).

John