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	Tue, 03 Dec 2024 12:21:37 -0500
Message-ID: <207d3b2abb0a9ead709de7b4710e256563b02f3b.camel@surriel.com>
Subject: Re: [RFC PATCH] smp: Evaluate local cond_func() before IPI
 side-effects
From: Rik van Riel <riel@surriel.com>
To: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: linux-kernel@vger.kernel.org, Peter Zijlstra <peterz@infradead.org>, 
 Ingo Molnar <mingo@kernel.org>, Dave Hansen <dave.hansen@intel.com>, Linus
 Torvalds	 <torvalds@linux-foundation.org>, Mel Gorman <mgorman@suse.de>,
 x86@kernel.org
Date: Tue, 03 Dec 2024 12:21:37 -0500
In-Reply-To: <20241203163558.3455535-1-mathieu.desnoyers@efficios.com>
References: <20241203163558.3455535-1-mathieu.desnoyers@efficios.com>
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On Tue, 2024-12-03 at 11:35 -0500, Mathieu Desnoyers wrote:
> In smp_call_function_many_cond(), the local cond_func() is evaluated
> after triggering the remote CPU IPIs.
>=20
> If cond_func() depends on loading shared state updated by other CPU's
> IPI handlers func(), then triggering execution of remote CPUs IPI
> before
> evaluating cond_func() may have unexpected consequences.
>=20
> One example scenario is evaluating a jiffies delay in cond_func(),
> which
> is updated by func() in the IPI handlers. This situation can prevent
> execution of periodic cleanup code on the local CPU.
>=20
> Link: https://lore.kernel.org/lkml/20241202202213.26a79ed6@fangorn/
> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
>=20

Reviewed-by: Rik van Riel <riel@surriel.com>

--=20
All Rights Reversed.