Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Fri, 13 Dec 2002 10:46:49 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Fri, 13 Dec 2002 10:46:49 -0500 Received: from tolkor.SGI.COM ([198.149.18.6]:36767 "EHLO tolkor.sgi.com") by vger.kernel.org with ESMTP id ; Fri, 13 Dec 2002 10:46:48 -0500 Date: Fri, 13 Dec 2002 18:08:14 -0500 From: Christoph Hellwig To: marcelo@conectiva.com.br Cc: rml@tech9.net, linux-kernel@vger.kernel.org Subject: Re: [PATCH] set_cpus_allowed() for 2.4 Message-ID: <20021213180814.A2658@sgi.com> Mail-Followup-To: Christoph Hellwig , marcelo@conectiva.com.br, rml@tech9.net, linux-kernel@vger.kernel.org Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2899 Lines: 90 Hi Marcelo, now that all vendors ship a backport of Ingo's O(1) scheduler, external projects like XFS have to track those trees in addition to the mainline kernel. Having the common new APIs available in mainline would be a very good thing to have for us and others. Now that 2.4.20 already has a working yield() the biggest missing part is set_cpus_allowed() to limit (kernel-)threads to a specific CPU or set of CPUs. --- linux/include/linux/sched.h~ Mon Sep 30 17:41:22 2002 +++ linux/include/linux/sched.h Tue Oct 1 18:35:28 2002 @@ -163,6 +164,12 @@ extern int start_context_thread(void); extern int current_is_keventd(void); +#if CONFIG_SMP +extern void set_cpus_allowed(struct task_struct *p, unsigned long new_mask); +#else +# define set_cpus_allowed(p, new_mask) do { } while (0) +#endif + /* * The default fd array needs to be at least BITS_PER_LONG, * as this is the granularity returned by copy_fdset(). --- linux/kernel/ksyms.c~ Mon Sep 30 17:41:22 2002 +++ linux/kernel/ksyms.c Tue Oct 1 18:34:41 2002 @@ -451,6 +451,9 @@ EXPORT_SYMBOL(interruptible_sleep_on_timeout); EXPORT_SYMBOL(schedule); EXPORT_SYMBOL(schedule_timeout); +#if CONFIG_SMP +EXPORT_SYMBOL(set_cpus_allowed); +#endif EXPORT_SYMBOL(yield); EXPORT_SYMBOL(__cond_resched); EXPORT_SYMBOL(jiffies); --- linux/kernel/sched.c~ Mon Sep 30 17:41:22 2002 +++ linux/kernel/sched.c Tue Oct 1 18:54:49 2002 @@ -850,6 +850,45 @@ void scheduling_functions_end_here(void) { } +#if CONFIG_SMP +/** + * set_cpus_allowed() - change a given task's processor affinity + * @p: task to bind + * @new_mask: bitmask of allowed processors + * + * Upon return, the task is running on a legal processor. Note the caller + * must have a valid reference to the task: it must not exit() prematurely. + * This call can sleep; do not hold locks on call. + */ +void set_cpus_allowed(struct task_struct *p, unsigned long new_mask) +{ + new_mask &= cpu_online_map; + BUG_ON(!new_mask); + + p->cpus_allowed = new_mask; + + /* + * If the task is on a no-longer-allowed processor, we need to move + * it. If the task is not current, then set need_resched and send + * its processor an IPI to reschedule. + */ + if (!(p->cpus_runnable & p->cpus_allowed)) { + if (p != current) { + p->need_resched = 1; + smp_send_reschedule(p->processor); + } + + /* + * Wait until we are on a legal processor. If the task is + * current, then we should be on a legal processor the next + * time we reschedule. Otherwise, we need to wait for the IPI. + */ + while (!(p->cpus_runnable & p->cpus_allowed)) + schedule(); + } +} +#endif /* CONFIG_SMP */ + #ifndef __alpha__ /* - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/