x86/mce: Fix RCU lockdep splats

Create an rcu_dereference_check_mce() that checks for RCU-sched
read side and mce_read_mutex being held on update side.  Replace
uses of rcu_dereference() in arch/x86/kernel/cpu/mcheck/mce.c
with this new macro.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: mathieu.desnoyers@polymtl.ca
Cc: josh@joshtriplett.org
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
Cc: Valdis.Kletnieks@vt.edu
Cc: dhowells@redhat.com
LKML-Reference: <1267830207-9474-3-git-send-email-paulmck@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 8 insertions, 3 deletions

diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index a8aacd4b513c..4442e9e898c2 100644
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -46,6 +46,11 @@
 
 #include "mce-internal.h"
 
+#define rcu_dereference_check_mce(p) \
+        rcu_dereference_check((p), \
+                              rcu_read_lock_sched_held() || \
+                              lockdep_is_held(&mce_read_mutex))
+
 #define CREATE_TRACE_POINTS
 #include <trace/events/mce.h>
 
@@ -158,7 +163,7 @@ void mce_log(struct mce *mce)
         mce->finished = 0;
         wmb();
         for (;;) {
-                entry = rcu_dereference(mcelog.next);
+                entry = rcu_dereference_check_mce(mcelog.next);
                 for (;;) {
                         /*
                          * When the buffer fills up discard new entries.
@@ -1500,7 +1505,7 @@ static ssize_t mce_read(struct file *filp, char __user *ubuf, size_t usize,
                 return -ENOMEM;
 
         mutex_lock(&mce_read_mutex);
-        next = rcu_dereference(mcelog.next);
+        next = rcu_dereference_check_mce(mcelog.next);
 
         /* Only supports full reads right now */
         if (*off != 0 || usize < MCE_LOG_LEN*sizeof(struct mce)) {
@@ -1565,7 +1570,7 @@ timeout:
 static unsigned int mce_poll(struct file *file, poll_table *wait)
 {
         poll_wait(file, &mce_wait, wait);
-        if (rcu_dereference(mcelog.next))
+        if (rcu_dereference_check_mce(mcelog.next))
                 return POLLIN | POLLRDNORM;
         return 0;
 }