Messages in this thread Patch in this message | | | From | Rusty Russell <> | Date | Thu Oct 23 11:55:16 EST 2008 | Subject | [PATCH 1/7] work_on_cpu: helper for doing task on a CPU. |
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Several places in the kernel do the following:
saved_mask = current->cpus_allowed; set_cpus_allowed_ptr(current, &cpumask_of_cpu(pr->id)); somefunc(); /* restore the previous state */ set_cpus_allowed_ptr(current, &saved_mask);
This is bad, because a process's cpumask is observable and manipulatable by userspace and should not be toyed with.
We have the infrastructure, this just creates a nice wrapper to encourage its use.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Cc: Ingo Molnar <mingo@elte.hu> --- include/linux/workqueue.h | 8 +++++++ kernel/workqueue.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 56 insertions(+)
diff -r b72e0cbdd249 include/linux/workqueue.h --- a/include/linux/workqueue.h Thu Oct 23 00:39:36 2008 +1100 +++ b/include/linux/workqueue.h Thu Oct 23 10:53:51 2008 +1100 @@ -240,4 +240,12 @@ void cancel_rearming_delayed_work(struct cancel_delayed_work_sync(work); } +#ifndef CONFIG_SMP +static inline long work_on_cpu(unsigned int cpu, long (*fn)(void *), void *arg) +{ + return fn(arg); +} +#else +long work_on_cpu(unsigned int cpu, long (*fn)(void *), void *arg); +#endif /* CONFIG_SMP */ #endif diff -r b72e0cbdd249 kernel/workqueue.c --- a/kernel/workqueue.c Thu Oct 23 00:39:36 2008 +1100 +++ b/kernel/workqueue.c Thu Oct 23 10:53:51 2008 +1100 @@ -970,6 +970,54 @@ undo: return ret; } +#ifdef CONFIG_SMP +struct work_for_cpu { + struct work_struct work; + long (*fn)(void *); + void *arg; + long ret; + struct completion done; +}; + +static void do_work_for_cpu(struct work_struct *w) +{ + struct work_for_cpu *wfc = container_of(w, struct work_for_cpu, work); + + wfc->ret = wfc->fn(wfc->arg); + complete(&wfc->done); +} + +/** + * work_on_cpu - run a function in user context on a particular cpu + * @cpu: the cpu to run on + * @fn: the function to run + * @arg: the function arg + * + * This will return -EINVAL in the cpu is not online, or the return value + * of @fn otherwise. + */ +long work_on_cpu(unsigned int cpu, long (*fn)(void *), void *arg) +{ + struct work_for_cpu wfc; + + INIT_WORK(&wfc.work, do_work_for_cpu); + init_completion(&wfc.done); + wfc.fn = fn; + wfc.arg = arg; + get_online_cpus(); + if (unlikely(!cpu_online(cpu))) { + wfc.ret = -EINVAL; + complete(&wfc.done); + } else + schedule_work_on(cpu, &wfc.work); + put_online_cpus(); + wait_for_completion(&wfc.done); + + return wfc.ret; +} +EXPORT_SYMBOL_GPL(work_on_cpu); +#endif /* CONFIG_SMP */ + void __init init_workqueues(void) { cpu_populated_map = cpu_online_map;
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