From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1952049AbdDYR2t (ORCPT ); Tue, 25 Apr 2017 13:28:49 -0400 Received: from Galois.linutronix.de ([146.0.238.70]:49157 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S971400AbdDYR2l (ORCPT ); Tue, 25 Apr 2017 13:28:41 -0400 Date: Tue, 25 Apr 2017 19:28:38 +0200 From: Sebastian Siewior To: Mark Rutland , Peter Zijlstra Cc: Thomas Gleixner , LKML , Ingo Molnar , Steven Rostedt , catalin.marinas@arm.com, will.deacon@arm.com, suzuki.poulose@arm.com, linux-arm-kernel@lists.infradead.org Subject: Re: [patch V2 00/24] cpu/hotplug: Convert get_online_cpus() to a percpu_rwsem Message-ID: <20170425172838.mr3kyccsdteyjso5@linutronix.de> References: <20170418170442.665445272@linutronix.de> <20170425161037.GA27156@leverpostej> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20170425161037.GA27156@leverpostej> User-Agent: NeoMutt/20170306 (1.8.0) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2017-04-25 17:10:37 [+0100], Mark Rutland wrote: > Hi, Hi, > When we bring the secondary CPU online, we detect an erratum that wasn't > present on the boot CPU, and try to enable a static branch we use to > track the erratum. The call to static_branch_enable() blows up as above. this (cpus_set_cap()) seems only to be used used in CPU up part. > I see that we now have static_branch_disable_cpuslocked(), but we don't > have an equivalent for enable. I'm not sure what we should be doing > here. We should introduce static_branch_enable_cpuslocked(). Does this work for you (after s/static_branch_enable/static_branch_enable_cpuslocked/ in cpus_set_cap()) ?: >>From fe004351e4649da037d5165247e89ab976fe4a26 Mon Sep 17 00:00:00 2001 From: Sebastian Andrzej Siewior Date: Tue, 25 Apr 2017 18:43:00 +0200 Subject: [PATCH] jump_label: Provide static_key_[enable|/slow_inc]_cpuslocked() Provide static_key_[enable|slow_inc]_cpuslocked() variant that don't take cpu_hotplug_lock(). Signed-off-by: Sebastian Andrzej Siewior --- include/linux/jump_label.h | 7 +++++++ kernel/jump_label.c | 10 ++++++++++ 2 files changed, 17 insertions(+) diff --git a/include/linux/jump_label.h b/include/linux/jump_label.h index d7b17d1ab875..c80d8b1279b5 100644 --- a/include/linux/jump_label.h +++ b/include/linux/jump_label.h @@ -164,6 +164,7 @@ extern void static_key_slow_dec_cpuslocked(struct static_key *key); extern void jump_label_apply_nops(struct module *mod); extern int static_key_count(struct static_key *key); extern void static_key_enable(struct static_key *key); +extern void static_key_enable_cpuslocked(struct static_key *key); extern void static_key_disable(struct static_key *key); extern void static_key_disable_cpuslocked(struct static_key *key); @@ -252,6 +253,11 @@ static inline void static_key_enable(struct static_key *key) static_key_slow_inc(key); } +static inline void static_key_enable_cpuslocked(struct static_key *key) +{ + static_key_enable(key); +} + static inline void static_key_disable(struct static_key *key) { int count = static_key_count(key); @@ -429,6 +435,7 @@ extern bool ____wrong_branch_error(void); */ #define static_branch_enable(x) static_key_enable(&(x)->key) +#define static_branch_enable_cpuslocked(x) static_key_enable_cpuslocked(&(x)->key) #define static_branch_disable(x) static_key_disable(&(x)->key) #define static_branch_disable_cpuslocked(x) static_key_disable_cpuslocked(&(x)->key) diff --git a/kernel/jump_label.c b/kernel/jump_label.c index d71124ee3b14..6343f4c7e27f 100644 --- a/kernel/jump_label.c +++ b/kernel/jump_label.c @@ -90,6 +90,16 @@ void static_key_enable(struct static_key *key) } EXPORT_SYMBOL_GPL(static_key_enable); +void static_key_enable_cpuslocked(struct static_key *key) +{ + int count = static_key_count(key); + + WARN_ON_ONCE(count < 0 || count > 1); + + if (!count) + static_key_slow_inc_cpuslocked(key); +} + void static_key_disable(struct static_key *key) { int count = static_key_count(key); -- 2.11.0 > Thanks, > Mark. Sebastian