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authorCorey Minyard <cminyard@mvista.com>2015-02-19 08:25:49 -0600
committerCorey Minyard <cminyard@mvista.com>2015-02-19 20:58:42 -0600
commit1d86e29b4a612eb01c39daa48749ab7964e77e03 (patch)
tree8fc87a38ad0b05994db7eefcb58ea4ac085deb25 /drivers/char
parentd6c5dc18d863338528f4e89e8dba9449c6e30f4e (diff)
ipmi: Fix a memory ordering issue
From a locking point of view it is safe to check waiting_msg without a lock, but there is a memory ordering issue that causes it to possibly not be set right when viewed from another processor. We are already claiming a lock right after that, move the check to inside the lock to enforce the memory ordering. Signed-off-by: Corey Minyard <cminyard@mvista.com>
Diffstat (limited to 'drivers/char')
-rw-r--r--drivers/char/ipmi/ipmi_si_intf.c14
1 files changed, 10 insertions, 4 deletions
diff --git a/drivers/char/ipmi/ipmi_si_intf.c b/drivers/char/ipmi/ipmi_si_intf.c
index 321ecb26df6a..f6646ed3047e 100644
--- a/drivers/char/ipmi/ipmi_si_intf.c
+++ b/drivers/char/ipmi/ipmi_si_intf.c
@@ -932,9 +932,6 @@ static void sender(void *send_info,
enum si_sm_result result;
unsigned long flags;
- BUG_ON(smi_info->waiting_msg);
- smi_info->waiting_msg = msg;
-
debug_timestamp("Enqueue");
if (smi_info->run_to_completion) {
@@ -942,7 +939,7 @@ static void sender(void *send_info,
* If we are running to completion, start it and run
* transactions until everything is clear.
*/
- smi_info->curr_msg = smi_info->waiting_msg;
+ smi_info->curr_msg = msg;
smi_info->waiting_msg = NULL;
/*
@@ -960,6 +957,15 @@ static void sender(void *send_info,
}
spin_lock_irqsave(&smi_info->si_lock, flags);
+ /*
+ * The following two lines don't need to be under the lock for
+ * the lock's sake, but they do need SMP memory barriers to
+ * avoid getting things out of order. We are already claiming
+ * the lock, anyway, so just do it under the lock to avoid the
+ * ordering problem.
+ */
+ BUG_ON(smi_info->waiting_msg);
+ smi_info->waiting_msg = msg;
check_start_timer_thread(smi_info);
spin_unlock_irqrestore(&smi_info->si_lock, flags);
}