From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ingo Molnar Subject: Re: [PATCH 3/5] watchdog: fix print-once on enable Date: Mon, 18 Aug 2014 11:05:29 +0200 Message-ID: <20140818090529.GB25495@gmail.com> References: <1407768567-171794-1-git-send-email-dzickus@redhat.com> <1407768567-171794-4-git-send-email-dzickus@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: akpm@linux-foundation.org, kvm@vger.kernel.org, pbonzini@redhat.com, mingo@redhat.com, LKML , Ulrich Obergfell , Andrew Jones To: Don Zickus Return-path: Content-Disposition: inline In-Reply-To: <1407768567-171794-4-git-send-email-dzickus@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org * Don Zickus wrote: > From: Ulrich Obergfell > > This patch avoids printing the message 'enabled on all CPUs, ...' > multiple times. For example, the issue can occur in the following > scenario: > > 1) watchdog_nmi_enable() fails to enable PMU counters and sets > cpu0_err. > > 2) 'echo [0|1] > /proc/sys/kernel/nmi_watchdog' is executed to > disable and re-enable the watchdog mechanism 'on the fly'. > > 3) If watchdog_nmi_enable() succeeds to enable PMU counters, each > CPU will print the message because step1 left behind a non-zero > cpu0_err. > > if (!IS_ERR(event)) { > if (cpu == 0 || cpu0_err) > pr_info("enabled on all CPUs, ...") > > The patch avoids this by clearing cpu0_err in watchdog_nmi_disable(). > > Signed-off-by: Ulrich Obergfell > Signed-off-by: Andrew Jones > Signed-off-by: Don Zickus > --- > kernel/watchdog.c | 3 +++ > 1 files changed, 3 insertions(+), 0 deletions(-) > > diff --git a/kernel/watchdog.c b/kernel/watchdog.c > index 6d0a891..0838685 100644 > --- a/kernel/watchdog.c > +++ b/kernel/watchdog.c > @@ -522,6 +522,9 @@ static void watchdog_nmi_disable(unsigned int cpu) > /* should be in cleanup, but blocks oprofile */ > perf_event_release_kernel(event); > } > + if (cpu == 0) > + /* watchdog_nmi_enable() expects this to be zero initially. */ > + cpu0_err = 0; Looks good except a small detail: two-line blocks need curly braces too, even if it's just a single C statement. I've fixed this up in the commit. thanks, Ingo