Before 69111bac42f5 ("powerpc: Replace __get_cpu_var uses"), in
save_mce_event, index got the value of mce_nest_count, and
mce_nest_count was incremented *after* index was set.
However, that patch changed the behaviour so that mce_nest count was
incremented *before* setting index.
This causes an off-by-one error, as get_mce_event sets index as
mce_nest_count - 1 before reading mce_event. Thus get_mce_event reads
bogus data, causing warnings like
"Machine Check Exception, Unknown event version 0 !"
and breaking MCEs handling.
Restore the old behaviour and unbreak MCE handling by moving the
increment to after index is set.
The same broken change occured in machine_check_queue_event (which set
a queue read by machine_check_process_queued_event). Fix that too,
unbreaking printing of MCE information.
Fixes: 69111bac42f5 ("powerpc: Replace __get_cpu_var uses")
CC: stable@xxxxxxxxxxxxxxx
CC: Mahesh Salgaonkar <mahesh@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Daniel Axtens <dja@xxxxxxxxxx>
---
arch/powerpc/kernel/mce.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/arch/powerpc/kernel/mce.c b/arch/powerpc/kernel/mce.c
index 15c99b6..f774b64 100644
--- a/arch/powerpc/kernel/mce.c
+++ b/arch/powerpc/kernel/mce.c
@@ -73,8 +73,9 @@ void save_mce_event(struct pt_regs *regs, long handled,
uint64_t nip, uint64_t addr)
{
uint64_t srr1;
- int index = __this_cpu_inc_return(mce_nest_count);
+ int index = __this_cpu_read(mce_nest_count);
struct machine_check_event *mce = this_cpu_ptr(&mce_event[index]);
+ __this_cpu_inc(mce_nest_count);
/*
* Return if we don't have enough space to log mce event.
@@ -184,7 +185,8 @@ void machine_check_queue_event(void)
if (!get_mce_event(&evt, MCE_EVENT_RELEASE))
return;
- index = __this_cpu_inc_return(mce_queue_count);
+ index = __this_cpu_read(mce_queue_count);
+ __this_cpu_inc(mce_queue_count);
/* If queue is full, just return for now. */
if (index >= MAX_MC_EVT) {
__this_cpu_dec(mce_queue_count);
--
2.1.4
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