From: Peter Zijlstra <firstname.lastname@example.org> To: "Rafael J. Wysocki" <email@example.com> Cc: Linux PM <firstname.lastname@example.org>, Daniel Lezcano <email@example.com>, Doug Smythies <firstname.lastname@example.org>, LKML <email@example.com> Subject: Re: [PATCH] cpuidle: Consolidate disabled state checks Date: Mon, 4 Nov 2019 12:52:01 +0100 [thread overview] Message-ID: <20191104115201.GG4131@hirez.programming.kicks-ass.net> (raw) In-Reply-To: <2717750.dCEzHT3DVQ@kreacher> On Mon, Nov 04, 2019 at 12:16:17PM +0100, Rafael J. Wysocki wrote: > From: Rafael J. Wysocki <firstname.lastname@example.org> > > There are two reasons why CPU idle states may be disabled: either > because the driver has disabled them or because they have been > disabled by user space via sysfs. > > In the former case, the state's "disabled" flag is set once during > the initialization of the driver and it is never cleared later (it > is read-only effectively). In the latter case, the "disable" field > of the given state's cpuidle_state_usage struct is set and it may be > changed via sysfs. Thus checking whether or not an idle state has > been disabled involves reading these two flags every time. > > In order to avoid the additional check of the state's "disabled" flag > (which is effectively read-only anyway), use the value of it at the > init time to set a (new) flag in the "disable" field of that state's > cpuidle_state_usage structure and use the sysfs interface to > manipulate another (new) flag in it. This way the state is disabled > whenever the "disable" field of its cpuidle_state_usage structure is > nonzero, whatever the reason, and it is the only place to look into > to check whether or not the state has been disabled. > > Signed-off-by: Rafael J. Wysocki <email@example.com> > Acked-by: Daniel Lezcano <firstname.lastname@example.org> Much thanks, that always bugged me. Acked-by: Peter Zijlstra (Intel) <email@example.com>
next prev parent reply other threads:[~2019-11-04 11:52 UTC|newest] Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-11-04 11:16 Rafael J. Wysocki 2019-11-04 11:52 ` Peter Zijlstra [this message] 2019-11-18 4:45 ` Len Brown 2019-11-18 9:22 ` Rafael J. Wysocki 2019-11-18 11:26 ` Rafael J. Wysocki 2019-11-18 23:04 ` [RFC][PATCH 0/2] cpuidle: Allow states to be disabled by default (was: Re: [PATCH] cpuidle: Consolidate disabled state checks) Rafael J. Wysocki 2019-11-18 23:07 ` [RFC][PATCH 1/2] cpuidle: Drop disabled field from struct cpuidle_state Rafael J. Wysocki 2019-11-18 23:09 ` [RFC][PATCH 2/2] cpuidle: Allow idle states to be disabled by default Rafael J. Wysocki
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