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authorSamuel Thibault <samuel.thibault@ens-lyon.org>2011-08-18 17:14:20 +0200
committerSamuel Thibault <samuel.thibault@ens-lyon.org>2011-08-18 17:14:20 +0200
commit26f79d5608fe5cf867559fef95d4ccdaaca1a994 (patch)
treed022c8c6ed6971fa4f1b7f149cac3c3a28893fc4
parente1f856119dae48fcc1b649521ca45e4bdaa80ea9 (diff)
Add compiler barrier to update_mapped_time
* kern/mach_clock.c (update_mapped_time): Add compiler barriers between writes to shared memory. Update comment: on SMP, write barriers are required.
-rw-r--r--kern/mach_clock.c4
1 files changed, 3 insertions, 1 deletions
diff --git a/kern/mach_clock.c b/kern/mach_clock.c
index 04a3115..4ba7c08 100644
--- a/kern/mach_clock.c
+++ b/kern/mach_clock.c
@@ -91,7 +91,7 @@ int bigadj = 1000000; /* adjust 10*tickadj if adjustment
* } while (secs != mtime->check_seconds);
* to read the time correctly. (On a multiprocessor this assumes
* that processors see each other's writes in the correct order.
- * We may have to insert fence operations.)
+ * We have to insert write fence operations.) FIXME
*/
mapped_time_value_t *mtime = 0;
@@ -100,7 +100,9 @@ mapped_time_value_t *mtime = 0;
MACRO_BEGIN \
if (mtime != 0) { \
mtime->check_seconds = (time)->seconds; \
+ asm volatile("":::"memory"); \
mtime->microseconds = (time)->microseconds; \
+ asm volatile("":::"memory"); \
mtime->seconds = (time)->seconds; \
} \
MACRO_END