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tests: Use exponential backoff in locked_vprintf()

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Without the exponential backoff a livelock was observed on a QorIQ P2020
with test SMP 5.
This commit is contained in:
Sebastian Huber
2017-11-22 09:40:24 +01:00
parent f64f7a2f29
commit c59479faa8
1 changed files with 19 additions and 3 deletions
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testsuites/support/src/locked_print.c
+19 -3
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@@ -14,7 +14,9 @@
#include "test_support.h"
#include "tmacros.h"
#include <unistd.h>
#include <rtems/bspIo.h>
#include <rtems/counter.h>
static rtems_id locked_print_semaphore; /* synchronisation semaphore */
@@ -62,9 +64,23 @@ int locked_vprintf(const char *fmt, va_list ap)
locked_print_initialize();
/* Lock semaphore without releasing the cpu */
do {
sc = rtems_semaphore_obtain( locked_print_semaphore, RTEMS_NO_WAIT, 0 );
} while (sc != RTEMS_SUCCESSFUL );
sc = rtems_semaphore_obtain( locked_print_semaphore, RTEMS_NO_WAIT, 0 );
if ( sc != RTEMS_SUCCESSFUL ) {
uint8_t e;
rtems_counter_ticks w;
/* Use exponential backoff to avoid a livelock */
getentropy( &e, sizeof( e ) );
w = e + 1;
do {
rtems_counter_delay_ticks( w );
w *= 2;
sc = rtems_semaphore_obtain( locked_print_semaphore, RTEMS_NO_WAIT, 0 );
} while (sc != RTEMS_SUCCESSFUL );
}
rv = vprintf(fmt, ap);