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From: Sebastian Siewior <bigeasy@linutronix.de>
To: Mark Rutland <mark.rutland@arm.com>,
	Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	LKML <linux-kernel@vger.kernel.org>,
	Ingo Molnar <mingo@kernel.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	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
Date: Tue, 25 Apr 2017 19:28:38 +0200
Message-ID: <20170425172838.mr3kyccsdteyjso5@linutronix.de> (raw)
In-Reply-To: <20170425161037.GA27156@leverpostej>

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 <bigeasy@linutronix.de>
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 <bigeasy@linutronix.de>
---
 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

  reply index

Thread overview: 72+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-04-18 17:04 Thomas Gleixner
2017-04-18 17:04 ` [patch V2 01/24] cpu/hotplug: Provide cpuhp_setup/remove_state[_nocalls]_cpuslocked() Thomas Gleixner
2017-04-20 11:18   ` [tip:smp/hotplug] " tip-bot for Sebastian Andrzej Siewior
2017-04-18 17:04 ` [patch V2 02/24] stop_machine: Provide stop_machine_cpuslocked() Thomas Gleixner
2017-04-20 11:19   ` [tip:smp/hotplug] " tip-bot for Sebastian Andrzej Siewior
2017-04-18 17:04 ` [patch V2 03/24] padata: Make padata_alloc() static Thomas Gleixner
2017-04-20 11:19   ` [tip:smp/hotplug] " tip-bot for Thomas Gleixner
2017-04-18 17:04 ` [patch V2 04/24] padata: Avoid nested calls to get_online_cpus() in pcrypt_init_padata() Thomas Gleixner
2017-04-20 11:20   ` [tip:smp/hotplug] " tip-bot for Sebastian Andrzej Siewior
2017-04-18 17:04 ` [patch V2 05/24] x86/mtrr: Remove get_online_cpus() from mtrr_save_state() Thomas Gleixner
2017-04-20 11:20   ` [tip:smp/hotplug] " tip-bot for Sebastian Andrzej Siewior
2017-04-18 17:04 ` [patch V2 06/24] cpufreq: Use cpuhp_setup_state_nocalls_cpuslocked() Thomas Gleixner
2017-04-20 11:21   ` [tip:smp/hotplug] " tip-bot for Sebastian Andrzej Siewior
2017-04-18 17:04 ` [patch V2 07/24] KVM/PPC/Book3S HV: " Thomas Gleixner
2017-04-20 11:21   ` [tip:smp/hotplug] " tip-bot for Sebastian Andrzej Siewior
2017-04-18 17:04 ` [patch V2 08/24] hwtracing/coresight-etm3x: " Thomas Gleixner
2017-04-20 11:22   ` [tip:smp/hotplug] " tip-bot for Sebastian Andrzej Siewior
2017-04-20 15:14   ` [patch V2 08/24] " Mathieu Poirier
2017-04-20 15:32   ` Mathieu Poirier
2017-04-18 17:04 ` [patch V2 09/24] hwtracing/coresight-etm4x: " Thomas Gleixner
2017-04-20 11:22   ` [tip:smp/hotplug] " tip-bot for Sebastian Andrzej Siewior
2017-04-18 17:04 ` [patch V2 10/24] perf/x86/intel/cqm: Use cpuhp_setup_state_cpuslocked() Thomas Gleixner
2017-04-20 11:23   ` [tip:smp/hotplug] " tip-bot for Sebastian Andrzej Siewior
2017-04-18 17:04 ` [patch V2 11/24] ARM/hw_breakpoint: " Thomas Gleixner
2017-04-19 17:54   ` Mark Rutland
2017-04-19 18:20     ` Thomas Gleixner
2017-04-20 11:23   ` [tip:smp/hotplug] " tip-bot for Sebastian Andrzej Siewior
2017-04-18 17:04 ` [patch V2 12/24] s390/kernel: Use stop_machine_cpuslocked() Thomas Gleixner
2017-04-20 11:24   ` [tip:smp/hotplug] " tip-bot for Sebastian Andrzej Siewior
2017-04-18 17:04 ` [patch V2 13/24] powerpc/powernv: " Thomas Gleixner
2017-04-20 11:24   ` [tip:smp/hotplug] " tip-bot for Sebastian Andrzej Siewior
2017-04-18 17:04 ` [patch V2 14/24] cpu/hotplug: Use stop_machine_cpuslocked() in takedown_cpu() Thomas Gleixner
2017-04-20 11:25   ` [tip:smp/hotplug] " tip-bot for Sebastian Andrzej Siewior
2017-04-18 17:04 ` [patch V2 15/24] x86/perf: Drop EXPORT of perf_check_microcode Thomas Gleixner
2017-04-20 11:25   ` [tip:smp/hotplug] " tip-bot for Thomas Gleixner
2017-04-18 17:04 ` [patch V2 16/24] perf/x86/intel: Drop get_online_cpus() in intel_snb_check_microcode() Thomas Gleixner
2017-04-20 11:26   ` [tip:smp/hotplug] " tip-bot for Sebastian Andrzej Siewior
2017-04-18 17:04 ` [patch V2 17/24] PCI: Use cpu_hotplug_disable() instead of get_online_cpus() Thomas Gleixner
2017-04-20 11:27   ` [tip:smp/hotplug] " tip-bot for Thomas Gleixner
2017-04-18 17:05 ` [patch V2 18/24] PCI: Replace the racy recursion prevention Thomas Gleixner
2017-04-20 11:27   ` [tip:smp/hotplug] " tip-bot for Thomas Gleixner
2017-04-18 17:05 ` [patch V2 19/24] ACPI/processor: Use cpu_hotplug_disable() instead of get_online_cpus() Thomas Gleixner
2017-04-20 11:28   ` [tip:smp/hotplug] " tip-bot for Thomas Gleixner
2017-04-18 17:05 ` [patch V2 20/24] perf/core: Remove redundant get_online_cpus() Thomas Gleixner
2017-04-20 11:28   ` [tip:smp/hotplug] " tip-bot for Thomas Gleixner
2017-04-18 17:05 ` [patch V2 21/24] jump_label: Pull get_online_cpus() into generic code Thomas Gleixner
2017-04-18 17:05 ` [patch V2 22/24] jump_label: Provide static_key_slow_inc_cpuslocked() Thomas Gleixner
2017-04-18 17:05 ` [patch V2 23/24] perf: Avoid cpu_hotplug_lock r-r recursion Thomas Gleixner
2017-04-18 17:05 ` [patch V2 24/24] cpu/hotplug: Convert hotplug locking to percpu rwsem Thomas Gleixner
2017-04-20 11:30   ` [tip:smp/hotplug] " tip-bot for Thomas Gleixner
2017-05-10  4:59   ` [patch V2 24/24] " Michael Ellerman
2017-05-10  8:49     ` Thomas Gleixner
2017-05-10 16:30       ` Steven Rostedt
2017-05-10 17:15         ` Steven Rostedt
2017-05-11  5:49       ` Michael Ellerman
2017-04-25 16:10 ` [patch V2 00/24] cpu/hotplug: Convert get_online_cpus() to a percpu_rwsem Mark Rutland
2017-04-25 17:28   ` Sebastian Siewior [this message]
2017-04-26  8:59     ` Mark Rutland
2017-04-26  9:40       ` Suzuki K Poulose
2017-04-26 10:32         ` Mark Rutland
2017-04-27  8:27           ` Sebastian Siewior
2017-04-27  9:57             ` Mark Rutland
2017-04-27 10:01               ` Thomas Gleixner
2017-04-27 12:30                 ` Mark Rutland
2017-04-27 15:48                   ` [PATCH] arm64: cpufeature: use static_branch_enable_cpuslocked() (was: Re: [patch V2 00/24] cpu/hotplug: Convert get_online_cpus() to a percpu_rwsem) Mark Rutland
2017-04-27 16:35                     ` Suzuki K Poulose
2017-04-27 17:03                       ` [PATCH] arm64: cpufeature: use static_branch_enable_cpuslocked() Suzuki K Poulose
2017-04-27 17:17                         ` Mark Rutland
2017-04-28 14:24 ` [RFC PATCH] trace/perf: cure locking issue in perf_event_open() error path Sebastian Siewior
2017-04-28 14:27   ` Sebastian Siewior
2017-05-01 12:57   ` [tip:smp/hotplug] perf: Reorder cpu hotplug rwsem against cred_guard_mutex tip-bot for Thomas Gleixner
2017-05-01 12:58   ` [tip:smp/hotplug] perf: Push hotplug protection down to callers tip-bot for Thomas Gleixner

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