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Message-ID: <372364b33b8d4b93908c3822e18f7d295de2ede9.camel@kernel.org>
Date: Wed, 18 May 2022 17:09:55 +0200
From: nicolas saenz julienne <nsaenz@...nel.org>
To: Frederic Weisbecker <frederic@...nel.org>,
LKML <linux-kernel@...r.kernel.org>
Cc: Peter Zijlstra <peterz@...radead.org>,
Phil Auld <pauld@...hat.com>,
Alex Belits <abelits@...vell.com>,
Xiongfeng Wang <wangxiongfeng2@...wei.com>,
Neeraj Upadhyay <quic_neeraju@...cinc.com>,
Thomas Gleixner <tglx@...utronix.de>,
Yu Liao <liaoyu15@...wei.com>,
Boqun Feng <boqun.feng@...il.com>,
"Paul E . McKenney" <paulmck@...nel.org>,
Marcelo Tosatti <mtosatti@...hat.com>,
Paul Gortmaker <paul.gortmaker@...driver.com>,
Uladzislau Rezki <uladzislau.rezki@...y.com>,
Joel Fernandes <joel@...lfernandes.org>
Subject: Re: [PATCH 20/21] context_tracking: Convert state to atomic_t
On Tue, 2022-05-03 at 12:00 +0200, Frederic Weisbecker wrote:
[...]
> +/**
> + * ct_state() - return the current context tracking state if known
> + *
> + * Returns the current cpu's context tracking state if context tracking
> + * is enabled. If context tracking is disabled, returns
> + * CONTEXT_DISABLED. This should be used primarily for debugging.
> + */
> +static __always_inline int ct_state(void)
> +{
> + int ret;
> +
> + if (!context_tracking_enabled())
> + return CONTEXT_DISABLED;
> +
> + preempt_disable();
> + ret = __ct_state();
> + preempt_enable();
> +
> + return ret;
> +}
> +
I can't see any use for this function with preemption enabled. You can't trust
the data due to CPU migration and it could be a source of bugs in the future.
Wouldn't it make more sense to move the burden into the callers? They all DTRT,
plus, this_cpu_ptr() will spew warnings if someone shows up and doesn't comply.
Regards,
--
Nicolás Sáenz
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