On Thu, Nov 08, 2007 at 03:48:05PM -0800, [EMAIL PROTECTED] wrote:
> With CONFIG_FAIR_CGROUP_SCHED=y, following commands on 2.6.24-rc1 crash
> the system.

Thanks for reporting the problem. It was caused because of the fact that
current task isn't kept in its runqueue in case of sched_fair class
tasks.

With the patch below, I could run ns_exec w/o any crash. Can you pls
verify it works for you as well?

Ingo,
        Once Suka verifies that the patch fixes his crash, I would request you 
to include the same in your tree and route it to Linus.

--

current task is not present in its runqueue in case of sched_fair class
tasks. Take care of this fact in rt_mutex_setprio(),
sched_setscheduler() and sched_move_task() routines.

Signed-off-by : Srivatsa Vaddagiri <[EMAIL PROTECTED]>


---
 kernel/sched.c |   45 +++++++++++++++++++++++++--------------------
 1 files changed, 25 insertions(+), 20 deletions(-)

Index: current/kernel/sched.c
===================================================================
--- current.orig/kernel/sched.c
+++ current/kernel/sched.c
@@ -3986,11 +3986,13 @@ void rt_mutex_setprio(struct task_struct
        oldprio = p->prio;
        on_rq = p->se.on_rq;
        running = task_running(rq, p);
-       if (on_rq) {
+       if (on_rq)
                dequeue_task(rq, p, 0);
-               if (running)
-                       p->sched_class->put_prev_task(rq, p);
-       }
+       /* current task is not kept in its runqueue in case of sched_fair class.
+        * Hence we need the 'on_rq?' and 'running?' tests to be separate.
+        */
+       if (running)
+               p->sched_class->put_prev_task(rq, p);
 
        if (rt_prio(prio))
                p->sched_class = &rt_sched_class;
@@ -3999,9 +4001,9 @@ void rt_mutex_setprio(struct task_struct
 
        p->prio = prio;
 
+       if (running)
+               p->sched_class->set_curr_task(rq);
        if (on_rq) {
-               if (running)
-                       p->sched_class->set_curr_task(rq);
                enqueue_task(rq, p, 0);
                inc_load(rq, p);
                /*
@@ -4298,18 +4300,20 @@ recheck:
        update_rq_clock(rq);
        on_rq = p->se.on_rq;
        running = task_running(rq, p);
-       if (on_rq) {
+       if (on_rq)
                deactivate_task(rq, p, 0);
-               if (running)
-                       p->sched_class->put_prev_task(rq, p);
-       }
+       /* current task is not kept in its runqueue in case of sched_fair class.
+        * Hence we need the 'on_rq?' and 'running?' tests to be separate.
+        */
+       if (running)
+               p->sched_class->put_prev_task(rq, p);
 
        oldprio = p->prio;
        __setscheduler(rq, p, policy, param->sched_priority);
 
+       if (running)
+               p->sched_class->set_curr_task(rq);
        if (on_rq) {
-               if (running)
-                       p->sched_class->set_curr_task(rq);
                activate_task(rq, p, 0);
                /*
                 * Reschedule if we are currently running on this runqueue and
@@ -7036,19 +7040,20 @@ void sched_move_task(struct task_struct 
        running = task_running(rq, tsk);
        on_rq = tsk->se.on_rq;
 
-       if (on_rq) {
+       if (on_rq)
                dequeue_task(rq, tsk, 0);
-               if (unlikely(running))
-                       tsk->sched_class->put_prev_task(rq, tsk);
-       }
+       /* current task is not kept in its runqueue in case of sched_fair class.
+        * Hence we need the 'on_rq?' and 'running?' tests to be separate.
+        */
+       if (unlikely(running))
+               tsk->sched_class->put_prev_task(rq, tsk);
 
        set_task_cfs_rq(tsk);
 
-       if (on_rq) {
-               if (unlikely(running))
-                       tsk->sched_class->set_curr_task(rq);
+       if (unlikely(running))
+               tsk->sched_class->set_curr_task(rq);
+       if (on_rq)
                enqueue_task(rq, tsk, 0);
-       }
 
 done:
        task_rq_unlock(rq, &flags);


-- 
Regards,
vatsa
-
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