2020-04-22 11:35:10

by Peter Zijlstra

Subject: [PATCH 18/23] sched,locktorture: Convert to sched_set_fifo()

Because SCHED_FIFO is a broken scheduler model (see previous patches)
take away the priority field, the kernel can't possibly make an
informed decision.

Effectively changes prio from 99 to 50.

Cc: [email protected]
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Reviewed-by: Ingo Molnar <[email protected]>
---
kernel/locking/locktorture.c | 10 ++--------
1 file changed, 2 insertions(+), 8 deletions(-)

--- a/kernel/locking/locktorture.c
+++ b/kernel/locking/locktorture.c
@@ -436,8 +436,6 @@ static int torture_rtmutex_lock(void) __

static void torture_rtmutex_boost(struct torture_random_state *trsp)
{
- int policy;
- struct sched_param param;
const unsigned int factor = 50000; /* yes, quite arbitrary */

if (!rt_task(current)) {
@@ -448,8 +446,7 @@ static void torture_rtmutex_boost(struct
*/
if (trsp && !(torture_random(trsp) %
(cxt.nrealwriters_stress * factor))) {
- policy = SCHED_FIFO;
- param.sched_priority = MAX_RT_PRIO - 1;
+ sched_set_fifo(current);
} else /* common case, do nothing */
return;
} else {
@@ -462,13 +459,10 @@ static void torture_rtmutex_boost(struct
*/
if (!trsp || !(torture_random(trsp) %
(cxt.nrealwriters_stress * factor * 2))) {
- policy = SCHED_NORMAL;
- param.sched_priority = 0;
+ sched_set_normal(current, 0);
} else /* common case, do nothing */
return;
}
-
- sched_setscheduler_nocheck(current, policy, &param);
}

static void torture_rtmutex_delay(struct torture_random_state *trsp)

2020-04-22 15:53:26

by Paul E. McKenney

Subject: Re: [PATCH 18/23] sched,locktorture: Convert to sched_set_fifo()

On Wed, Apr 22, 2020 at 01:27:37PM +0200, Peter Zijlstra wrote:
> Because SCHED_FIFO is a broken scheduler model (see previous patches)
> take away the priority field, the kernel can't possibly make an
> informed decision.
>
> Effectively changes prio from 99 to 50.
>
> Cc: [email protected]
> Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
> Reviewed-by: Ingo Molnar <[email protected]>

Reviewed-by: Paul E. McKenney <[email protected]>

> ---
> kernel/locking/locktorture.c | 10 ++--------
> 1 file changed, 2 insertions(+), 8 deletions(-)
>
> --- a/kernel/locking/locktorture.c
> +++ b/kernel/locking/locktorture.c
> @@ -436,8 +436,6 @@ static int torture_rtmutex_lock(void) __
>
> static void torture_rtmutex_boost(struct torture_random_state *trsp)
> {
> - int policy;
> - struct sched_param param;
> const unsigned int factor = 50000; /* yes, quite arbitrary */
>
> if (!rt_task(current)) {
> @@ -448,8 +446,7 @@ static void torture_rtmutex_boost(struct
> */
> if (trsp && !(torture_random(trsp) %
> (cxt.nrealwriters_stress * factor))) {
> - policy = SCHED_FIFO;
> - param.sched_priority = MAX_RT_PRIO - 1;
> + sched_set_fifo(current);
> } else /* common case, do nothing */
> return;
> } else {
> @@ -462,13 +459,10 @@ static void torture_rtmutex_boost(struct
> */
> if (!trsp || !(torture_random(trsp) %
> (cxt.nrealwriters_stress * factor * 2))) {
> - policy = SCHED_NORMAL;
> - param.sched_priority = 0;
> + sched_set_normal(current, 0);
> } else /* common case, do nothing */
> return;
> }
> -
> - sched_setscheduler_nocheck(current, policy, &param);
> }
>
> static void torture_rtmutex_delay(struct torture_random_state *trsp)
>
>