mmstress: make shared global variables volatile

PATCH In review Jan Stancek 2 participants 2 messages Mar 13, 2012

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Jan Stancek

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2012-03-13 10:32 UTC #0 lore raw

PATCH 1/1 mmstress: make shared global variables volatile

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 <[email protected]>

---
 testcases/kernel/mem/mtest05/mmstress.c |    6 +++---
 1 files changed, 3 insertions(+), 3 deletions(-)

testcases/kernel/mem/mtest05/mmstress.c +3 -3

index 8a0c6f6..a8d4e7d 100644
@@ -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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Wanlong Gao

2012-03-13 12:10 UTC #1 lore raw

Quoted 9 lines · Jan Stancek

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.

Quoted 8 lines

See also:
Bug 36081 - gcc optimizations and threads (pthread)
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36081
Signed-off-by Jan Stancek <[email protected]>
---
 testcases/kernel/mem/mtest05/mmstress.c |    6 +++---
 1 files changed, 3 insertions(+), 3 deletions(-)

pushed, thanks Jan.

Wanlong Gao

Quoted 13 lines

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Quoted 4 lines

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