linux-kernel - [PATCH 1/8] x86, mce: stop calling del_timer

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Date:	Fri, 17 Jun 2011 17:40:36 +0900
From:	Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>
To:	linux-kernel@...r.kernel.org
CC:	"x86@...nel.org" <x86@...nel.org>, Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	"Luck, Tony" <tony.luck@...el.com>, Borislav Petkov <bp@...64.org>
Subject: [PATCH 1/8] x86, mce: stop calling del_timer_sync() from interrupt

Function del_timer_sync() has WARN_ON(in_irq()) in it because
calling it from interrupt context can cause deadlock if it
interrupts the target timer running.

In MCE code, del_timer_sync() is used with on_each_cpu() in
some parts for sysfs files:
  bank*, check_interval, cmci_disabled and ignore_ce.

However use of on_each_cpu() results in calling the function
passed as the argument in the interrupt context.  It means you
can see a flood of warnings from del_timer_sync() by a simple
file access, for example:

  echo 300 > /sys/devices/system/machinecheck/machinecheck0/check_interval

Fortunately these MCE specific files are rare-used and AFAIK
only few MCE geeks experience this warning on write.

To remove the warning (for my happy hacking), move timer deletion
outside of the interrupt context ;-)

v2: update patch description

Signed-off-by: Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>
---
 arch/x86/kernel/cpu/mcheck/mce.c |   22 ++++++++++++++++------
 1 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index 08363b0..42fc8d2 100644
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -1140,6 +1140,17 @@ static void mce_start_timer(unsigned long data)
 	add_timer_on(t, smp_processor_id());
 }
 
+/* Must not be called from interrupt where del_timer_sync() can deadlock */
+static void mce_timer_delete_all(void)
+{
+	int cpu;
+
+	for_each_online_cpu(cpu) {
+		if (mce_available(&per_cpu(cpu_info, cpu)))
+			del_timer_sync(&per_cpu(mce_timer, cpu));
+	}
+}
+
 static void mce_do_trigger(struct work_struct *work)
 {
 	call_usermodehelper(mce_helper, mce_helper_argv, NULL, UMH_NO_WAIT);
@@ -1750,7 +1761,6 @@ static struct syscore_ops mce_syscore_ops = {
 
 static void mce_cpu_restart(void *data)
 {
-	del_timer_sync(&__get_cpu_var(mce_timer));
 	if (!mce_available(__this_cpu_ptr(&cpu_info)))
 		return;
 	__mcheck_cpu_init_generic();
@@ -1760,16 +1770,15 @@ static void mce_cpu_restart(void *data)
 /* Reinit MCEs after user configuration changes */
 static void mce_restart(void)
 {
+	mce_timer_delete_all();
 	on_each_cpu(mce_cpu_restart, NULL, 1);
 }
 
 /* Toggle features for corrected errors */
-static void mce_disable_ce(void *all)
+static void mce_disable_cmci(void *data)
 {
 	if (!mce_available(__this_cpu_ptr(&cpu_info)))
 		return;
-	if (all)
-		del_timer_sync(&__get_cpu_var(mce_timer));
 	cmci_clear();
 }
 
@@ -1852,7 +1861,8 @@ static ssize_t set_ignore_ce(struct sys_device *s,
 	if (mce_ignore_ce ^ !!new) {
 		if (new) {
 			/* disable ce features */
-			on_each_cpu(mce_disable_ce, (void *)1, 1);
+			mce_timer_delete_all();
+			on_each_cpu(mce_disable_cmci, NULL, 1);
 			mce_ignore_ce = 1;
 		} else {
 			/* enable ce features */
@@ -1875,7 +1885,7 @@ static ssize_t set_cmci_disabled(struct sys_device *s,
 	if (mce_cmci_disabled ^ !!new) {
 		if (new) {
 			/* disable cmci */
-			on_each_cpu(mce_disable_ce, NULL, 1);
+			on_each_cpu(mce_disable_cmci, NULL, 1);
 			mce_cmci_disabled = 1;
 		} else {
 			/* enable cmci */
-- 
1.7.1


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