[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: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/arch/s390/include/asm/sigp.h b/arch/s390/include/asm/sigp.h
index e3bffd4..7040b85 100644
--- a/arch/s390/include/asm/sigp.h
+++ b/arch/s390/include/asm/sigp.h
@@ -56,6 +56,7 @@
ec_schedule = 0,
ec_call_function,
ec_call_function_single,
+ ec_stop_cpu,
};
/*
diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c
index 8aba77d..b1cd329 100644
--- a/arch/s390/kernel/smp.c
+++ b/arch/s390/kernel/smp.c
@@ -154,22 +154,52 @@
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 @@
*/
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 @@
if (test_bit(ec_call_function_single, &bits))
generic_smp_call_function_single_interrupt();
+
}
/*