[PATCH 4/5] SMP01: possible CPU race when using byte arrays

[Daniel Hellstrom]

Bool is char, a 4 CPU 8-bit variable array will crate a race, where CPU1 might over write CPU2 and CPU3 task execution status. There is no atomic locking of the TaskRan array.

Daniel

On 10/31/2013 03:17 PM, Gedare Bloom wrote:
> I don't understand the problem being solved here / the reason for this
> change from bool to int.
>
> On Thu, Oct 31, 2013 at 9:58 AM, Daniel Hellstrom <daniel at gaisler.com> wrote:
>> Switch to using 32-bit variable that works better on a
>> 32-bit CPU. This does not solve the general SMP case
>> though, would perhaps better to use an atomic set
>> here.
>>
>> Signed-off-by: Daniel Hellstrom <daniel at gaisler.com>
>> ---
>>   testsuites/smptests/smp01/init.c   |    6 +++---
>>   testsuites/smptests/smp01/system.h |    2 +-
>>   testsuites/smptests/smp01/tasks.c  |    2 +-
>>   3 files changed, 5 insertions(+), 5 deletions(-)
>>
>> diff --git a/testsuites/smptests/smp01/init.c b/testsuites/smptests/smp01/init.c
>> index 3e12726..eadb26a 100644
>> --- a/testsuites/smptests/smp01/init.c
>> +++ b/testsuites/smptests/smp01/init.c
>> @@ -43,11 +43,11 @@ rtems_task Init(
>>     locked_print_initialize();
>>
>>     /* Put start of test message */
>> -  locked_printf( "\n\n***  SMP01 TEST ***\n" );
>> +  locked_printf( "\n\n***  SMP01 TEST %d ***\n", cpu_self );
>>
>>     /* Initialize the TaskRan array */
>>     for ( i=0; i<rtems_smp_get_processor_count() ; i++ ) {
>> -    TaskRan[i] = false;
>> +    TaskRan[i] = 0;
>>     }
>>
>>     /* Create and start tasks for each processor */
>> @@ -77,7 +77,7 @@ rtems_task Init(
>>     while (1) {
>>       allDone = true;
>>       for ( i=0; i<rtems_smp_get_processor_count() ; i++ ) {
>> -      if ( i != cpu_self && TaskRan[i] == false)
>> +      if ( i != cpu_self && TaskRan[i] == 0)
>>           allDone = false;
>>       }
>>       if (allDone) {
>> diff --git a/testsuites/smptests/smp01/system.h b/testsuites/smptests/smp01/system.h
>> index e360e37..5f2d5b7 100644
>> --- a/testsuites/smptests/smp01/system.h
>> +++ b/testsuites/smptests/smp01/system.h
>> @@ -42,7 +42,7 @@ rtems_task Test_task(
>>    *  Keep the names and IDs in global variables so another task can use them.
>>    */
>>
>> -TEST_EXTERN volatile bool TaskRan[ CONFIGURE_SMP_MAXIMUM_PROCESSORS ];
>> +TEST_EXTERN volatile int TaskRan[ CONFIGURE_SMP_MAXIMUM_PROCESSORS ];
>>
>>   void Loop( void );
>>
>> diff --git a/testsuites/smptests/smp01/tasks.c b/testsuites/smptests/smp01/tasks.c
>> index 4eb81f1..7bd7cc4 100644
>> --- a/testsuites/smptests/smp01/tasks.c
>> +++ b/testsuites/smptests/smp01/tasks.c
>> @@ -35,7 +35,7 @@ rtems_task Test_task(
>>     locked_printf(" CPU %" PRIu32 " running Task %s\n", cpu_num, name);
>>
>>     /* Set the flag that the task is up and running */
>> -  TaskRan[cpu_num] = true;
>> +  TaskRan[cpu_num] = 1;
>>
>>
>>     /* Drop into a loop which will keep this task on
>> --
>> 1.7.0.4
>>
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