linux-kernel - Re: Query regarding synchronize_sched_expedited and resched

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Message-ID: <20170918111105.15f687da@gandalf.local.home>
Date:   Mon, 18 Sep 2017 11:11:05 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Neeraj Upadhyay <neeraju@...eaurora.org>
Cc:     paulmck@...ux.vnet.ibm.com, josh@...htriplett.org,
        mathieu.desnoyers@...icios.com, jiangshanlai@...il.com,
        linux-kernel@...r.kernel.org, sramana@...eaurora.org,
        prsood@...eaurora.org, pkondeti@...eaurora.org,
        markivx@...eaurora.org, peterz@...radead.org
Subject: Re: Query regarding synchronize_sched_expedited and resched_cpu

On Sun, 17 Sep 2017 11:37:06 +0530
Neeraj Upadhyay <neeraju@...eaurora.org> wrote:

> Hi Paul, how about replacing raw_spin_trylock_irqsave with
> raw_spin_lock_irqsave in resched_cpu()? Are there any paths
> in RCU code, which depend on trylock check/spinlock recursion?

It looks to me that resched_cpu() was added for nohz full sched
balancing, but is not longer used by that. The only user is currently
RCU. Perhaps we should change that from a trylock to a lock.

-- Steve