Messages in this thread Patch in this message |  | | | Subject | [PATCH] set_cpus_allowed() for 2.4 | | From | Robert Love <> | | Date | 01 Oct 2002 19:03:28 -0400 |
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The following patch implements set_cpus_allowed() for stock 2.4 without the O(1) scheduler.
The calling semantics and behavior remain the same as 2.5's method.
This is to provide a backward-compatible interface, specifically for those interested in back-porting the new workqueue code to 2.4 - set_cpus_allowed() seems to be the only nit preventing a straight drop-in.
Patch is against 2.4.20-pre8 and untested but does compile.
Robert Love
diff -urN linux-2.4.20-pre8/include/linux/sched.h linux/include/linux/sched.h --- linux-2.4.20-pre8/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(). diff -urN linux-2.4.20-pre8/kernel/ksyms.c linux/kernel/ksyms.c --- linux-2.4.20-pre8/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); diff -urN linux-2.4.20-pre8/kernel/sched.c linux/kernel/sched.c --- linux-2.4.20-pre8/kernel/sched.c Mon Sep 30 17:41:22 2002 +++ linux/kernel/sched.c Tue Oct 1 18:54:49 2002 @@ -850,6 +850,46 @@ 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__ /* diff -urN linux-2.4.20-pre8/kernel/softirq.c linux/kernel/softirq.c --- linux-2.4.20-pre8/kernel/softirq.c Mon Sep 30 17:41:22 2002 +++ linux/kernel/softirq.c Tue Oct 1 18:53:01 2002 @@ -368,9 +368,8 @@ sigfillset(¤t->blocked); /* Migrate to the right CPU */ - current->cpus_allowed = 1UL << cpu; - while (smp_processor_id() != cpu) - schedule(); + set_cpus_allowed(current, 1UL << cpu); + BUG_ON(smp_processor_id() != cpu); sprintf(current->comm, "ksoftirqd_CPU%d", bind_cpu);
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