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s390/smp: smp_emergency_stop() - move cpumask away from stack

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Make "cpumask_t cpumask" a static variable to avoid a potential large
stack frame. Also protect against potential concurrent callers by
introducing a local lock.
Note: smp_emergency_stop() gets only called with irqs and machine
checks disabled, therefore a cpu local deadlock is not possible. For
concurrent callers the first cpu which enters the critical section
wins and will stop all other cpus.

Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
This commit is contained in:
Heiko Carstens 2021-02-17 07:19:09 +01:00 committed by Vasily Gorbik
parent 62c8dca9e1
commit f213e5502d
1 changed files with 4 additions and 1 deletions
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5
arch/s390/kernel/smp.c
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@ -434,10 +434,12 @@ void notrace smp_yield_cpu(int cpu)
*/
void notrace smp_emergency_stop(void)
{
cpumask_t cpumask;
static arch_spinlock_t lock = __ARCH_SPIN_LOCK_UNLOCKED;
static cpumask_t cpumask;
u64 end;
int cpu;
arch_spin_lock(&lock);
cpumask_copy(&cpumask, cpu_online_mask);
cpumask_clear_cpu(smp_processor_id(), &cpumask);
@ -458,6 +460,7 @@ void notrace smp_emergency_stop(void)
break;
cpu_relax();
}
arch_spin_unlock(&lock);
}
NOKPROBE_SYMBOL(smp_emergency_stop);