linux-kernel - Re: [PATCH RFC] rcu/kfree: Do not request RCU when not needed

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Message-Id: <ED8E1017-A219-4815-BA28-5F44A2FB8FF2@joelfernandes.org>
Date:   Wed, 2 Nov 2022 15:51:49 -0400
From:   Joel Fernandes <joel@...lfernandes.org>
To:     paulmck@...nel.org
Cc:     Uladzislau Rezki <urezki@...il.com>, rcu@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC] rcu/kfree: Do not request RCU when not needed



> On Nov 2, 2022, at 2:32 PM, Paul E. McKenney <paulmck@...nel.org> wrote:
> 
> On Wed, Nov 02, 2022 at 06:30:24PM +0100, Uladzislau Rezki wrote:
>>> 
>>> to wait for a GP. Or if the poll_state_synchronize_rcu(oldstate)) != 0
>>> queue_rcu_work().
>>> 
>> A small fix. If poll_state_synchronize_rcu(oldstate)) == 0 then
>> queue_rcu_work() since a GP is still in progress.
> 
> Both get_state_synchronize_rcu() and poll_state_synchronize_rcu()
> may be invoked from interrupt handlers.  And from NMI handlers,
> for that matter.

Thanks for clarifying. I meant to say cond_synchronize_rcu() cannot be called from interrupt context, but I made that comment before Vlad cooked his patch.

Thanks,

 - Joel


>                            Thanx, Paul