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Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1fkTtV-0002W5-EH; Tue, 31 Jul 2018 12:36:53 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 8A6E82027585B; Tue, 31 Jul 2018 14:36:51 +0200 (CEST) Date: Tue, 31 Jul 2018 14:36:51 +0200 From: Peter Zijlstra To: jiada_wang@mentor.com Cc: mingo@redhat.com, linux-kernel@vger.kernel.org, george_davis@mentor.com, erosca@de.adit-jv.com Subject: Re: [PATCH v2 1/1] sched/debug: fix potential deadlock when write to sched_features Message-ID: <20180731123651.GW2494@hirez.programming.kicks-ass.net> References: <20180731121222.26195-1-jiada_wang@mentor.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180731121222.26195-1-jiada_wang@mentor.com> User-Agent: Mutt/1.10.0 (2018-05-17) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jul 31, 2018 at 09:12:22PM +0900, jiada_wang@mentor.com wrote: > diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c > index 60caf1fb94e0..7b2997d4a349 100644 > --- a/kernel/sched/debug.c > +++ b/kernel/sched/debug.c > @@ -87,21 +87,21 @@ struct static_key sched_feat_keys[__SCHED_FEAT_NR] = { > > #undef SCHED_FEAT > > -static void sched_feat_disable(int i) > +static void sched_feat_disable_cpuslocked(int i) > { > - static_key_disable(&sched_feat_keys[i]); > + static_key_disable_cpuslocked(&sched_feat_keys[i]); > } > > -static void sched_feat_enable(int i) > +static void sched_feat_enable_cpuslocked(int i) > { > - static_key_enable(&sched_feat_keys[i]); > + static_key_enable_cpuslocked(&sched_feat_keys[i]); > } > #else > -static void sched_feat_disable(int i) { }; > -static void sched_feat_enable(int i) { }; > +static void sched_feat_disable_cpuslocked(int i) { }; > +static void sched_feat_enable_cpuslocked(int i) { }; > #endif /* HAVE_JUMP_LABEL */ > > -static int sched_feat_set(char *cmp) > +static int sched_feat_set_cpuslocked(char *cmp) > { > int i; > int neg = 0; > @@ -117,10 +117,10 @@ static int sched_feat_set(char *cmp) > > if (neg) { > sysctl_sched_features &= ~(1UL << i); > - sched_feat_disable(i); > + sched_feat_disable_cpuslocked(i); > } else { > sysctl_sched_features |= (1UL << i); > - sched_feat_enable(i); > + sched_feat_enable_cpuslocked(i); > } > > return 0; > @@ -146,9 +146,11 @@ sched_feat_write(struct file *filp, const char __user *ubuf, > > /* Ensure the static_key remains in a consistent state */ > inode = file_inode(filp); > + cpus_read_lock(); > inode_lock(inode); > - ret = sched_feat_set(cmp); > + ret = sched_feat_set_cpuslocked(cmp); > inode_unlock(inode); > + cpus_read_unlock(); > if (ret < 0) > return ret; > I've made that.. --- --- a/kernel/sched/debug.c +++ b/kernel/sched/debug.c @@ -89,12 +89,12 @@ struct static_key sched_feat_keys[__SCHE static void sched_feat_disable(int i) { - static_key_disable(&sched_feat_keys[i]); + static_key_disable_cpuslocked(&sched_feat_keys[i]); } static void sched_feat_enable(int i) { - static_key_enable(&sched_feat_keys[i]); + static_key_enable_cpuslocked(&sched_feat_keys[i]); } #else static void sched_feat_disable(int i) { }; @@ -146,9 +146,11 @@ sched_feat_write(struct file *filp, cons /* Ensure the static_key remains in a consistent state */ inode = file_inode(filp); + cpus_read_lock(); inode_lock(inode); ret = sched_feat_set(cmp); inode_unlock(inode); + cpus_read_unlock(); if (ret < 0) return ret;