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

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

[Jan Stancek]

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

[Wanlong Gao]

On 03/13/2012 06:32 PM, Jan Stancek wrote:

> 
> 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(-)


pushed, thanks Jan.

Wanlong Gao

> 
> 
> 
> 
> ------------------------------------------------------------------------------
> Keep Your Developer Skills Current with LearnDevNow!
> The most comprehensive online learning library for Microsoft developers
> is just $99.99! Visual Studio, SharePoint, SQL - plus HTML5, CSS3, MVC3,
> Metro Style Apps, more. Free future releases when you subscribe now!
> http://p.sf.net/sfu/learndevnow-d2d
> 
> 
> 
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> Ltp-list mailing list
> Ltp-list@lists.sourceforge.net
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