From: Thomas Gleixner <tglx@linutronix.de>
To: Michael Ellerman <mpe@ellerman.id.au>
Cc: LKML <linux-kernel@vger.kernel.org>,
Ingo Molnar <mingo@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Borislav Petkov <bp@alien8.de>,
Andrew Morton <akpm@linux-foundation.org>,
Sebastian Siewior <bigeasy@linutronix.de>,
Nicholas Piggin <npiggin@gmail.com>,
Don Zickus <dzickus@redhat.com>,
Chris Metcalf <cmetcalf@mellanox.com>,
Ulrich Obergfell <uobergfe@redhat.com>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
linuxppc-dev@lists.ozlabs.org
Subject: Re: [patch V2 22/29] lockup_detector: Make watchdog_nmi_reconfigure() two stage
Date: Tue, 3 Oct 2017 08:50:59 +0200 (CEST) [thread overview]
Message-ID: <alpine.DEB.2.20.1710030848210.2281@nanos> (raw)
In-Reply-To: <87d165dqew.fsf@concordia.ellerman.id.au>
On Tue, 3 Oct 2017, Michael Ellerman wrote:
> Hi Thomas,
> Unfortunately this is hitting the WARN_ON in start_wd_cpu() on powerpc
> because we're calling it multiple times for the boot CPU.
>
> The first call is via:
>
> start_wd_on_cpu+0x80/0x2f0
> watchdog_nmi_reconfigure+0x124/0x170
> softlockup_reconfigure_threads+0x110/0x130
> lockup_detector_init+0xbc/0xe0
> kernel_init_freeable+0x18c/0x37c
> kernel_init+0x2c/0x160
> ret_from_kernel_thread+0x5c/0xbc
>
> And then again via the CPU hotplug registration:
>
> start_wd_on_cpu+0x80/0x2f0
> cpuhp_invoke_callback+0x194/0x620
> cpuhp_thread_fun+0x7c/0x1b0
> smpboot_thread_fn+0x290/0x2a0
> kthread+0x168/0x1b0
> ret_from_kernel_thread+0x5c/0xbc
>
>
> The first call is new because previously watchdog_nmi_reconfigure()
> wasn't called from softlockup_reconfigure_threads().
Hmm, don't you have the same problem with CPU hotplug or do you just get
lucky because the hotplug callback in your code is ordered vs. the
softlockup thread hotplug callback in a way that this does not hit?
> I'm not sure what the easiest fix is. One option would be to just drop
> the WARN_ON, it's just there for paranoia AFAICS.
The straight forward way is to make use of the new probe function. Patch
below.
Thanks,
tglx
8<------------------
--- a/arch/powerpc/kernel/watchdog.c
+++ b/arch/powerpc/kernel/watchdog.c
@@ -375,20 +375,18 @@ void watchdog_nmi_start(void)
/*
* This runs after lockup_detector_init() which sets up watchdog_cpumask.
*/
-static int __init powerpc_watchdog_init(void)
+int __init watchdog_nmi_probe(void)
{
int err;
- watchdog_calc_timeouts();
-
- err = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "powerpc/watchdog:online",
- start_wd_on_cpu, stop_wd_on_cpu);
+ err = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
+ "powerpc/watchdog:online",
+ start_wd_on_cpu, stop_wd_on_cpu);
if (err < 0)
pr_warn("Watchdog could not be initialized");
return 0;
}
-arch_initcall(powerpc_watchdog_init);
static void handle_backtrace_ipi(struct pt_regs *regs)
{
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -608,7 +608,6 @@ static inline int watchdog_park_threads(
static inline void watchdog_unpark_threads(void) { }
static inline int watchdog_enable_all_cpus(void) { return 0; }
static inline void watchdog_disable_all_cpus(void) { }
-static inline void softlockup_init_threads(void) { }
static void softlockup_reconfigure_threads(void)
{
cpus_read_lock();
@@ -617,6 +616,10 @@ static void softlockup_reconfigure_threa
watchdog_nmi_start();
cpus_read_unlock();
}
+static inline void softlockup_init_threads(void)
+{
+ softlockup_reconfigure_threads();
+}
#endif /* !CONFIG_SOFTLOCKUP_DETECTOR */
static void __lockup_detector_cleanup(void)
next prev parent reply other threads:[~2017-10-03 6:51 UTC|newest]
Thread overview: 77+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-12 19:36 [patch V2 00/29] lockup_detector: Cure hotplug deadlocks and replace duct tape Thomas Gleixner
2017-09-12 19:36 ` [patch V2 01/29] hardlockup_detector: Provide interface to stop/restart perf events Thomas Gleixner
2017-09-14 10:40 ` [tip:core/urgent] watchdog/hardlockup: " tip-bot for Peter Zijlstra
2017-09-12 19:36 ` [patch V2 02/29] perf/x86/intel: Sanitize PMU HT bug workaround Thomas Gleixner
2017-09-14 10:40 ` [tip:core/urgent] perf/x86/intel, watchdog/core: " tip-bot for Peter Zijlstra
2017-09-12 19:36 ` [patch V2 03/29] lockup_detector: Provide interface to stop from poweroff() Thomas Gleixner
2017-09-14 10:40 ` [tip:core/urgent] watchdog/core: " tip-bot for Thomas Gleixner
2017-09-12 19:36 ` [patch V2 04/29] parisc: Use lockup_detector_stop() Thomas Gleixner
2017-09-14 8:59 ` Helge Deller
2017-09-14 13:46 ` Don Zickus
2017-09-14 10:41 ` [tip:core/urgent] parisc, watchdog/core: " tip-bot for Thomas Gleixner
2017-09-12 19:36 ` [patch V2 05/29] lockup_detector: Remove broken suspend/resume interfaces Thomas Gleixner
2017-09-14 10:41 ` [tip:core/urgent] watchdog/core: " tip-bot for Thomas Gleixner
2017-09-12 19:37 ` [patch V2 06/29] lockup_detector: Rework cpu hotplug locking Thomas Gleixner
2017-09-14 10:41 ` [tip:core/urgent] watchdog/core: Rework CPU " tip-bot for Thomas Gleixner
2017-09-12 19:37 ` [patch V2 07/29] lockup_detector: Rename watchdog_proc_mutex Thomas Gleixner
2017-09-14 10:42 ` [tip:core/urgent] watchdog/core: " tip-bot for Thomas Gleixner
2017-09-12 19:37 ` [patch V2 08/29] lockup_detector: Mark hardlockup_detector_disable() __init Thomas Gleixner
2017-09-14 10:42 ` [tip:core/urgent] watchdog/core: " tip-bot for Thomas Gleixner
2017-09-12 19:37 ` [patch V2 09/29] lockup_detector/perf: Remove broken self disable on failure Thomas Gleixner
2017-09-14 10:43 ` [tip:core/urgent] watchdog/hardlockup/perf: " tip-bot for Thomas Gleixner
2017-09-12 19:37 ` [patch V2 10/29] lockup_detector/perf: Prevent cpu hotplug deadlock Thomas Gleixner
2017-09-14 10:43 ` [tip:core/urgent] watchdog/hardlockup/perf: Prevent CPU " tip-bot for Thomas Gleixner
2017-09-12 19:37 ` [patch V2 11/29] lockup_detector: Remove park_in_progress obfuscation Thomas Gleixner
2017-09-12 19:37 ` [patch V2 12/29] lockup_detector: Cleanup stub functions Thomas Gleixner
2017-09-14 10:44 ` [tip:core/urgent] watchdog/core: Clean up " tip-bot for Thomas Gleixner
2017-09-12 19:37 ` [patch V2 13/29] lockup_detector: Cleanup the ifdef maze Thomas Gleixner
2017-09-14 10:44 ` [tip:core/urgent] watchdog/core: Clean up the #ifdef maze tip-bot for Thomas Gleixner
2017-09-12 19:37 ` [patch V2 14/29] lockup_detector: Split out cpumask write function Thomas Gleixner
2017-09-14 10:45 ` [tip:core/urgent] watchdog/core: " tip-bot for Thomas Gleixner
2017-09-12 19:37 ` [patch V2 15/29] smpboot/threads: Avoid runtime allocation Thomas Gleixner
2017-09-14 10:45 ` [tip:core/urgent] smpboot/threads, watchdog/core: " tip-bot for Thomas Gleixner
2017-09-12 19:37 ` [patch V2 16/29] lockup_detector: Create new thread handling infrastructure Thomas Gleixner
2017-09-14 10:45 ` [tip:core/urgent] watchdog/core: " tip-bot for Thomas Gleixner
2017-09-12 19:37 ` [patch V2 17/29] lockup_detector: Get rid of the thread teardown/setup dance Thomas Gleixner
2017-09-14 10:46 ` [tip:core/urgent] watchdog/core: " tip-bot for Thomas Gleixner
2017-09-12 19:37 ` [patch V2 18/29] lockup_detector: Further simplify sysctl handling Thomas Gleixner
2017-09-14 10:46 ` [tip:core/urgent] watchdog/core: " tip-bot for Thomas Gleixner
2017-09-12 19:37 ` [patch V2 19/29] lockup_detector: Cleanup header mess Thomas Gleixner
2017-09-14 10:47 ` [tip:core/urgent] watchdog/core: Clean up " tip-bot for Thomas Gleixner
2017-09-12 19:37 ` [patch V2 20/29] lockup_detector/sysctl: Get rid of the ifdeffery Thomas Gleixner
2017-09-14 10:47 ` [tip:core/urgent] watchdog/sysctl: Get rid of the #ifdeffery tip-bot for Thomas Gleixner
2017-09-12 19:37 ` [patch V2 21/29] lockup_detector: Cleanup sysctl variable name space Thomas Gleixner
2017-09-14 10:47 ` [tip:core/urgent] watchdog/sysctl: Clean up " tip-bot for Thomas Gleixner
2017-09-12 19:37 ` [patch V2 22/29] lockup_detector: Make watchdog_nmi_reconfigure() two stage Thomas Gleixner
2017-09-14 10:48 ` [tip:core/urgent] watchdog/core, powerpc: " tip-bot for Thomas Gleixner
2017-10-03 0:29 ` [patch V2 22/29] lockup_detector: " Michael Ellerman
2017-10-03 6:50 ` Thomas Gleixner [this message]
2017-10-03 7:04 ` Thomas Gleixner
2017-10-03 10:01 ` Nicholas Piggin
2017-10-03 10:56 ` Thomas Gleixner
2017-10-03 11:36 ` Michael Ellerman
2017-10-03 12:13 ` Thomas Gleixner
2017-10-03 13:20 ` Thomas Gleixner
2017-10-03 19:27 ` Thomas Gleixner
2017-10-04 5:53 ` Michael Ellerman
2017-10-05 16:17 ` Don Zickus
2017-09-12 19:37 ` [patch V2 23/29] lockup_detector: Get rid of the racy update loop Thomas Gleixner
2017-09-14 10:48 ` [tip:core/urgent] watchdog/core: " tip-bot for Thomas Gleixner
2017-09-12 19:37 ` [patch V2 24/29] lockup_detector/perf: Implement init time perf validation Thomas Gleixner
2017-09-14 10:48 ` [tip:core/urgent] watchdog/hardlockup/perf: " tip-bot for Thomas Gleixner
2017-09-12 19:37 ` [patch V2 25/29] lockup_detector: Implement init time detection of perf Thomas Gleixner
2017-09-13 18:02 ` Don Zickus
2017-09-13 18:05 ` Thomas Gleixner
2017-09-14 5:27 ` Ingo Molnar
2017-09-14 10:49 ` [tip:core/urgent] watchdog/hardlockup/perf: " tip-bot for Thomas Gleixner
2017-09-12 19:37 ` [patch V2 26/29] lockup_detector/perf: Implement CPU enable replacement Thomas Gleixner
2017-09-14 10:49 ` [tip:core/urgent] watchdog/hardlockup/perf: " tip-bot for Thomas Gleixner
2017-09-12 19:37 ` [patch V2 27/29] lockup_detector: Use new perf CPU enable mechanism Thomas Gleixner
2017-09-14 10:50 ` [tip:core/urgent] watchdog/hardlockup/perf: " tip-bot for Thomas Gleixner
2017-09-12 19:37 ` [patch V2 28/29] lockup_detector/perf: Simplify deferred event destroy Thomas Gleixner
2017-09-14 10:50 ` [tip:core/urgent] watchdog/hardlockup/perf: " tip-bot for Thomas Gleixner
2017-09-12 19:37 ` [patch V2 29/29] lockup_detector: Cleanup hotplug locking mess Thomas Gleixner
2017-09-14 10:50 ` [tip:core/urgent] watchdog/hardlockup: Clean up " tip-bot for Thomas Gleixner
2017-09-13 18:06 ` [patch V2 00/29] lockup_detector: Cure hotplug deadlocks and replace duct tape Don Zickus
2017-09-14 5:27 ` Ingo Molnar
2017-09-14 8:11 ` Thomas Gleixner
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