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smpboot/threads, watchdog/core: Avoid runtime allocation

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smpboot_update_cpumask_threads_percpu() allocates a temporary cpumask at
runtime. This is suboptimal because the call site needs more code size for
proper error handling than a statically allocated temporary mask requires
data size.

Add static temporary cpumask. The function is globaly serialized, so no
further protection required.

Remove the half baken error handling in the watchdog code and get rid of
the export as there are no in tree modular users of that function.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Don Zickus <dzickus@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: Ulrich Obergfell <uobergfe@redhat.com>
Link: http://lkml.kernel.org/r/20170912194147.297288838@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Thomas Gleixner 2017-09-12 21:37:09 +02:00 committed by Ingo Molnar
parent 05ba3de74a
commit 0d85923c7a
3 changed files with 14 additions and 33 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
include/linux/smpboot.h
View File

@ -55,7 +55,7 @@ smpboot_register_percpu_thread(struct smp_hotplug_thread *plug_thread)
}
void smpboot_unregister_percpu_thread(struct smp_hotplug_thread *plug_thread);
int smpboot_update_cpumask_percpu_thread(struct smp_hotplug_thread *plug_thread,
const struct cpumask *);
void smpboot_update_cpumask_percpu_thread(struct smp_hotplug_thread *plug_thread,
const struct cpumask *);
#endif

22
kernel/smpboot.c
View File

@ -344,39 +344,31 @@ EXPORT_SYMBOL_GPL(smpboot_unregister_percpu_thread);
* by the client, but only by calling this function.
* This function can only be called on a registered smp_hotplug_thread.
*/
int smpboot_update_cpumask_percpu_thread(struct smp_hotplug_thread *plug_thread,
const struct cpumask *new)
void smpboot_update_cpumask_percpu_thread(struct smp_hotplug_thread *plug_thread,
const struct cpumask *new)
{
struct cpumask *old = plug_thread->cpumask;
cpumask_var_t tmp;
static struct cpumask tmp;
unsigned int cpu;
if (!alloc_cpumask_var(&tmp, GFP_KERNEL))
return -ENOMEM;
get_online_cpus();
mutex_lock(&smpboot_threads_lock);
/* Park threads that were exclusively enabled on the old mask. */
cpumask_andnot(tmp, old, new);
for_each_cpu_and(cpu, tmp, cpu_online_mask)
cpumask_andnot(&tmp, old, new);
for_each_cpu_and(cpu, &tmp, cpu_online_mask)
smpboot_park_thread(plug_thread, cpu);
/* Unpark threads that are exclusively enabled on the new mask. */
cpumask_andnot(tmp, new, old);
for_each_cpu_and(cpu, tmp, cpu_online_mask)
cpumask_andnot(&tmp, new, old);
for_each_cpu_and(cpu, &tmp, cpu_online_mask)
smpboot_unpark_thread(plug_thread, cpu);
cpumask_copy(old, new);
mutex_unlock(&smpboot_threads_lock);
put_online_cpus();
free_cpumask_var(tmp);
return 0;
}
EXPORT_SYMBOL_GPL(smpboot_update_cpumask_percpu_thread);
static DEFINE_PER_CPU(atomic_t, cpu_hotplug_state) = ATOMIC_INIT(CPU_POST_DEAD);

21
kernel/watchdog.c
View File

@ -787,31 +787,20 @@ out:
return err;
}
static int watchdog_update_cpus(void)
static void watchdog_update_cpus(void)
{
if (IS_ENABLED(CONFIG_SOFTLOCKUP_DETECTOR)) {
return smpboot_update_cpumask_percpu_thread(&watchdog_threads,
&watchdog_cpumask);
if (IS_ENABLED(CONFIG_SOFTLOCKUP_DETECTOR) && watchdog_running) {
smpboot_update_cpumask_percpu_thread(&watchdog_threads,
&watchdog_cpumask);
__lockup_detector_cleanup();
}
return 0;
}
static void proc_watchdog_cpumask_update(void)
{
/* Remove impossible cpus to keep sysctl output clean. */
cpumask_and(&watchdog_cpumask, &watchdog_cpumask, cpu_possible_mask);
if (watchdog_running) {
/*
* Failure would be due to being unable to allocate a
* temporary cpumask, so we are likely not in a position to
* do much else to make things better.
*/
if (watchdog_update_cpus() != 0)
pr_err("cpumask update failed\n");
}
watchdog_update_cpus();
watchdog_nmi_reconfigure();
}