tracing, Text Edit Lock - SMP alternatives support

Use the mutual exclusion provided by the text edit lock in alternatives code.
Since alternative_smp_* will be called from module init code, etc,
we'd better protect it from other subsystems.

Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
LKML-Reference: <49B14332.9030109@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 5 insertions, 0 deletions

diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index 4c80f1557433..092a7b8be68d 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -5,6 +5,7 @@
 #include <linux/kprobes.h>
 #include <linux/mm.h>
 #include <linux/vmalloc.h>
+#include <linux/memory.h>
 #include <asm/alternative.h>
 #include <asm/sections.h>
 #include <asm/pgtable.h>
@@ -226,6 +227,7 @@ static void alternatives_smp_lock(u8 **start, u8 **end, u8 *text, u8 *text_end)
 {
         u8 **ptr;
 
+        mutex_lock(&text_mutex);
         for (ptr = start; ptr < end; ptr++) {
                 if (*ptr < text)
                         continue;
@@ -234,6 +236,7 @@ static void alternatives_smp_lock(u8 **start, u8 **end, u8 *text, u8 *text_end)
                 /* turn DS segment override prefix into lock prefix */
                 text_poke(*ptr, ((unsigned char []){0xf0}), 1);
         };
+        mutex_unlock(&text_mutex);
 }
 
 static void alternatives_smp_unlock(u8 **start, u8 **end, u8 *text, u8 *text_end)
@@ -243,6 +246,7 @@ static void alternatives_smp_unlock(u8 **start, u8 **end, u8 *text, u8 *text_end
         if (noreplace_smp)
                 return;
 
+        mutex_lock(&text_mutex);
         for (ptr = start; ptr < end; ptr++) {
                 if (*ptr < text)
                         continue;
@@ -251,6 +255,7 @@ static void alternatives_smp_unlock(u8 **start, u8 **end, u8 *text, u8 *text_end
                 /* turn lock prefix into DS segment override prefix */
                 text_poke(*ptr, ((unsigned char []){0x3E}), 1);
         };
+        mutex_unlock(&text_mutex);
 }
 
 struct smp_alt_module {