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Commit 85ac7ca5 authored by Martin Schwidefsky's avatar Martin Schwidefsky
Browse files

[S390] outstanding interrupts vs. smp_send_stop 



The panic function will first print the panic message to the console,
then stop additional cpus with smp_send_stop and finally call the
function on the panic notifier list.
In case of an I/O based console the panic message will cause I/O to
be started and a function on the panic notifier list will wait for the
completion of the I/O. That does not work if an I/O completion interrupt
has already been delivered to a cpu that is then stopped by smp_send_stop.
To break this cyclic dependency add code to smp_send_stop that gives
the additional cpu the opportunity to complete outstanding interrupts.

Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent 3a3954ce

arch/s390/include/asm/sigp.h

+1 −0
Original line number Diff line number Diff line
@@ -56,6 +56,7 @@ enum { 
	ec_schedule = 0,

	ec_call_function,

	ec_call_function_single,

	ec_stop_cpu,

};



/*

arch/s390/kernel/smp.c

+42 −8
Original line number Diff line number Diff line
@@ -154,22 +154,52 @@ void smp_switch_to_ipl_cpu(void (*func)(void *), void *data) 
	smp_switch_to_cpu(func, data, sp, stap(), __cpu_logical_map[0]);

}



static void smp_stop_cpu(void)

{

	while (sigp(smp_processor_id(), sigp_stop) == sigp_busy)

		cpu_relax();

}



void smp_send_stop(void)

{

	int cpu, rc;

	cpumask_t cpumask;

	int cpu;

	u64 end;



	/* Disable all interrupts/machine checks */

	__load_psw_mask(psw_kernel_bits | PSW_MASK_DAT);

	trace_hardirqs_off();



	/* stop all processors */

	for_each_online_cpu(cpu) {

		if (cpu == smp_processor_id())

			continue;

		do {

			rc = sigp(cpu, sigp_stop);

		} while (rc == sigp_busy);

	cpumask_copy(&cpumask, cpu_online_mask);

	cpumask_clear_cpu(smp_processor_id(), &cpumask);



	if (oops_in_progress) {

		/*

		 * Give the other cpus the opportunity to complete

		 * outstanding interrupts before stopping them.

		 */

		end = get_clock() + (1000000UL << 12);

		for_each_cpu(cpu, &cpumask) {

			set_bit(ec_stop_cpu, (unsigned long *)

				&lowcore_ptr[cpu]->ext_call_fast);

			while (sigp(cpu, sigp_emergency_signal) == sigp_busy &&

			       get_clock() < end)

				cpu_relax();

		}

		while (get_clock() < end) {

			for_each_cpu(cpu, &cpumask)

				if (cpu_stopped(cpu))

					cpumask_clear_cpu(cpu, &cpumask);

			if (cpumask_empty(&cpumask))

				break;

			cpu_relax();

		}

	}



	/* stop all processors */

	for_each_cpu(cpu, &cpumask) {

		while (sigp(cpu, sigp_stop) == sigp_busy)

			cpu_relax();

		while (!cpu_stopped(cpu))

			cpu_relax();

	}
@@ -194,6 +224,9 @@ static void do_ext_call_interrupt(unsigned int ext_int_code, 
	 */

	bits = xchg(&S390_lowcore.ext_call_fast, 0);



	if (test_bit(ec_stop_cpu, &bits))

		smp_stop_cpu();



	if (test_bit(ec_schedule, &bits))

		scheduler_ipi();
@@ -202,6 +235,7 @@ static void do_ext_call_interrupt(unsigned int ext_int_code, 


	if (test_bit(ec_call_function_single, &bits))

		generic_smp_call_function_single_interrupt();



}



/*