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Message-ID: <20071008124350.GA5779@elte.hu> Date: Mon, 8 Oct 2007 14:43:50 +0200 From: Ingo Molnar <mingo@...e.hu> To: Andi Kleen <ak@...e.de> Cc: linux-kernel@...r.kernel.org Subject: Re: [PATCH] [5/6] scheduler: Protect important kernel threads against normalize_rt * Andi Kleen <ak@...e.de> wrote: > softlockup is the same. Just think about it. > > If you ever renormalize it and then run a fifo thread it will starve > and then eventually kill the box. > > And starving CPU unplug is also equally bad. yeah, agreed. I ended up doing the change below. Ingo -------------------> Subject: sched: do not normalize kernel threads via SysRq-N From: Ingo Molnar <mingo@...e.hu> do not normalize kernel threads via SysRq-N: the migration threads, softlockup threads, etc. might be essential for the system to function properly. So only zap user tasks. pointed out by Andi Kleen. Signed-off-by: Ingo Molnar <mingo@...e.hu> --- kernel/sched.c | 18 +++++++----------- 1 file changed, 7 insertions(+), 11 deletions(-) Index: linux/kernel/sched.c =================================================================== --- linux.orig/kernel/sched.c +++ linux/kernel/sched.c @@ -362,15 +362,6 @@ static inline int cpu_of(struct rq *rq) #endif } -static inline int is_migration_thread(struct task_struct *p, struct rq *rq) -{ -#ifdef CONFIG_SMP - return p == rq->migration_thread; -#else - return 0; -#endif -} - /* * Update the per-runqueue clock, as finegrained as the platform can give * us, but without assuming monotonicity, etc.: @@ -6557,6 +6548,12 @@ void normalize_rt_tasks(void) read_lock_irq(&tasklist_lock); do_each_thread(g, p) { + /* + * Only normalize user tasks: + */ + if (!p->mm) + continue; + p->se.exec_start = 0; #ifdef CONFIG_SCHEDSTATS p->se.wait_start = 0; @@ -6578,8 +6575,7 @@ void normalize_rt_tasks(void) spin_lock_irqsave(&p->pi_lock, flags); rq = __task_rq_lock(p); - if (!is_migration_thread(p, rq)) - normalize_task(rq, p); + normalize_task(rq, p); __task_rq_unlock(rq); spin_unlock_irqrestore(&p->pi_lock, flags); - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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