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Commit 9aaef96f authored by Hidetoshi Seto's avatar Hidetoshi Seto Committed by Borislav Petkov
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x86, mce: Do not call del_timer_sync() in IRQ context 



del_timer_sync() can cause a deadlock when called in interrupt context.
It is used with on_each_cpu() in some parts for sysfs files like bank*,
check_interval, cmci_disabled and ignore_ce.

However, use of on_each_cpu() results in calling the function passed
as the argument in interrupt context. This causes a flood of nested
warnings from del_timer_sync() (it runs on each CPU) caused even by a
simple file access like:

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

Fortunately, these MCE-specific files are rarely used and AFAIK only few
MCE geeks experience this warning.

To remove the warning, move timer deletion outside of the interrupt
context.

Signed-off-by: default avatarHidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Signed-off-by: default avatarBorislav Petkov <borislav.petkov@amd.com>
parent b6fd41e2

arch/x86/kernel/cpu/mcheck/mce.c

+14 −6
Original line number Diff line number Diff line
@@ -1140,6 +1140,15 @@ static void mce_start_timer(unsigned long data) 
	add_timer_on(t, smp_processor_id());

}



/* Must not be called in IRQ context where del_timer_sync() can deadlock */

static void mce_timer_delete_all(void)

{

	int cpu;



	for_each_online_cpu(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 +1759,6 @@ 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 +1768,15 @@ 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 +1859,8 @@ 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 +1883,7 @@ 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 */