x86/intel_rdt/mbm: Fix MBM overflow handler during CPU hotplug

When a CPU is dying, the overflow worker is canceled and rescheduled on a
different CPU in the same domain. But if the timer is already about to
expire this essentially doubles the interval which might result in a non
detected overflow.

Cancel the overflow worker and reschedule it immediately on a different CPU
in same domain. The work could be flushed as well, but that would
reschedule it on the same CPU.

[ tglx: Rewrote changelog once again ]

Reported-by: Thomas Gleixner <[e-mail]>
Signed-off-by: Vikas Shivappa <[e-mail]>
Signed-off-by: Thomas Gleixner <[e-mail]>
Cc: [e-mail]
Cc: [e-mail]
Cc: [e-mail]
Cc: [e-mail]
Cc: [e-mail]
Cc: [e-mail]
Cc: [e-mail]
Cc: [e-mail]
Link: http://lkml.kernel.org/r/[e-mail]

arch/x86/kernel/cpu/intel_rdt.c

···
 
 	if (is_mbm_enabled()) {
 		INIT_DELAYED_WORK(&d->mbm_over, mbm_handle_overflow);
-		mbm_setup_overflow_handler(d);
+		mbm_setup_overflow_handler(d, MBM_OVERFLOW_INTERVAL);
 	}
 
 	return 0;
···
 	} else if (r == &rdt_resources_all[RDT_RESOURCE_L3] &&
 		   cpu == d->mbm_work_cpu && is_mbm_enabled()) {
 		cancel_delayed_work(&d->mbm_over);
-		mbm_setup_overflow_handler(d);
+		mbm_setup_overflow_handler(d, 0);
 	}
 }
 

arch/x86/kernel/cpu/intel_rdt.h

···
 				    struct rdt_domain *d);
 void mon_event_read(struct rmid_read *rr, struct rdt_domain *d,
 		    struct rdtgroup *rdtgrp, int evtid, int first);
-void mbm_setup_overflow_handler(struct rdt_domain *dom);
+void mbm_setup_overflow_handler(struct rdt_domain *dom, unsigned long delay_ms);
 void mbm_handle_overflow(struct work_struct *work);
 
 #endif /* _ASM_X86_INTEL_RDT_H */

arch/x86/kernel/cpu/intel_rdt_monitor.c

···
 	mutex_unlock(&rdtgroup_mutex);
 }
 
-void mbm_setup_overflow_handler(struct rdt_domain *dom)
+void mbm_setup_overflow_handler(struct rdt_domain *dom, unsigned long delay_ms)
 {
-	unsigned long delay = msecs_to_jiffies(MBM_OVERFLOW_INTERVAL);
+	unsigned long delay = msecs_to_jiffies(delay_ms);
 	int cpu;
 
 	if (!static_branch_likely(&rdt_enable_key))

arch/x86/kernel/cpu/intel_rdt_rdtgroup.c

···
 	if (is_mbm_enabled()) {
 		r = &rdt_resources_all[RDT_RESOURCE_L3];
 		list_for_each_entry(dom, &r->domains, list)
-			mbm_setup_overflow_handler(dom);
+			mbm_setup_overflow_handler(dom, MBM_OVERFLOW_INTERVAL);
 	}
 
 	goto out;