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Date:   Tue, 5 Dec 2023 19:29:24 +0100
From:   Sebastian Siewior <bigeasy@linutronix.de>
To:     Anna-Maria Behnsen <anna-maria@linutronix.de>
Cc:     linux-kernel@vger.kernel.org,
        Peter Zijlstra <peterz@infradead.org>,
        John Stultz <jstultz@google.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Eric Dumazet <edumazet@google.com>,
        "Rafael J . Wysocki" <rafael.j.wysocki@intel.com>,
        Arjan van de Ven <arjan@infradead.org>,
        "Paul E . McKenney" <paulmck@kernel.org>,
        Frederic Weisbecker <frederic@kernel.org>,
        Rik van Riel <riel@surriel.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Giovanni Gherdovich <ggherdovich@suse.cz>,
        Lukasz Luba <lukasz.luba@arm.com>,
        "Gautham R . Shenoy" <gautham.shenoy@amd.com>,
        Srinivas Pandruvada <srinivas.pandruvada@intel.com>,
        K Prateek Nayak <kprateek.nayak@amd.com>
Subject: Re: [PATCH v9 19/32] timers: add_timer_on(): Make sure TIMER_PINNED
 flag is set
Message-ID: <20231205182924.SFCmSKXe@linutronix.de>
References: <20231201092654.34614-1-anna-maria@linutronix.de>
 <20231201092654.34614-20-anna-maria@linutronix.de>
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On 2023-12-01 10:26:41 [+0100], Anna-Maria Behnsen wrote:
> When adding a timer to the timer wheel using add_timer_on(), it is an
> implicitly pinned timer. With the timer pull at expiry time model in plac=
e,
> TIMER_PINNED flag is required to make sure timers end up in proper base.
>=20
> Add TIMER_PINNED flag unconditionally when add_timer_on() is executed.

This is odd. I have some vague memory that this was already the case.
Otherwise all add_timer_on() users without TIMER_PINNED may get it wrong
due to optimisation. Looking at git history it was never the case and I
can't confuse it with hrtimer since it never supported the "_on()"
feature=E2=80=A6
At least the mix timer in drivers/char/random.c is not using the PINNED
flag with _on(). So this was wrong then?=E2=80=A6

Sebastian