[LTP] [PATCH] mmstress: make shared global variables volatile

Jan Stancek
2012-03-13T10:32:36Z

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Synchronization of threads depends on shared global variable.
With gcc version 4.6.2 this test spins forever on:
while (wait_thread)
sched_yield();

Make global shared variables volatile, so each thread
sees current value.

See also:
Bug 36081 - gcc optimizations and threads (pthread)
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36081

Signed-off-by: Jan Stancek <jstancek@redhat.com>
---
testcases/kernel/mem/mtest05/mmstress.c | 6 +++---
1 files changed, 3 insertions(+), 3 deletions(-)

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diff --git a/testcases/kernel/mem/mtest05/mmstress.c b/testcases/kernel/mem/mtest05/mmstress.c
index 8a0c6f6..a8d4e7d 100644
--- a/testcases/kernel/mem/mtest05/mmstress.c
+++ b/testcases/kernel/mem/mtest05/mmstress.c
@@ -140,8 +140,8 @@ typedef struct { /* structure returned by map_and_thread() */
caddr_t mapaddr; /* address at which the file is mapped */
} RETINFO_t;

-static int wait_thread = 0; /* used to wake up sleeping threads */
-static int thread_begin = 0; /* used to coordinate threads */
+static volatile int wait_thread = 0; /* used to wake up sleeping threads */
+static volatile int thread_begin = 0; /* used to coordinate threads */
static int verbose_print = FALSE; /* print more test information */

static int pages_num = NUMPAGES; /* number of pages to use for tests */
@@ -989,4 +989,4 @@ main(int argc, /* number of command line parameters */
tst_resm(TPASS, "Test Passed");
}
exit(global_rc);
-}
\ No newline at end of file
+}

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