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: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>

1 files changed, 14 insertions, 6 deletions

diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index 08363b04212..5b5cceec94c 100644
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -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 */