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Date: Wed, 11 Nov 2009 08:21:28 +0100 (CET) From: Thomas Gleixner <tglx@...utronix.de> To: Jupyung Lee <jupyung@...il.com> cc: LKML <linux-kernel@...r.kernel.org> Subject: Re: [PATCH-rt 1/1] softirqs: add preempt_check_resched() in ksoftirqd() Jupyung, On Wed, 11 Nov 2009, Jupyung Lee wrote: > In its current preempt-rt kernel, ksoftirq() includes a series of primitives > related with kernel preemption and irq on/off, in the following order: > > preempt_disable() ... (1) > local_irq_disable() ... (2) > __preempt_enable_no_resched() ... (3) > local_irq_enable() ... (4) > > A problem arises if a process is awakened between (1) and (2) because > it is not given a chance to preempt the currently running process > for a while since (4): since (4), the kernel is preemptible, but there > is no explicit reschedule point. > > A simple suggestion to resolve the problem is to add a reschedule point, > preempt_check_resched(), just after (4). Good catch. I applied it with a simple modification. Thanks, tglx --- commit ca0b4bfa5994856bbcf4227e29f9c73722efaef2 Author: Jupyung Lee <jupyung@...il.com> <snip> --- a/kernel/softirq.c +++ b/kernel/softirq.c @@ -1033,10 +1033,10 @@ sleep_more: goto sleep_more; } per_cpu(softirq_running, cpu) |= softirq_mask; - __preempt_enable_no_resched(); set_softirq_pending(local_softirq_pending() & ~softirq_mask); local_bh_disable(); local_irq_enable(); + preempt_enable(); h = &softirq_vec[data->nr]; if (h) -- 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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