OpenSDV
/
original_kernel
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

s390/smp: lost IPIs on cpu hotplug 

IPIs might be lost when a cpu gets brought offline:

When stop_machine executes its state machine there is a race window
for the state STOPMACHINE_DISABLE_IRQ where the to be brought offline
cpu might already have irqs disabled but a different cpu still may
have irqs enabled.
If the enabled cpu receives an interrupt and as a result sends an IPI
to the to be offlined cpu in its bottom halve context, the IPI won't
be noticed before the cpu is offline.

In fact the race window is much larger since there is no guarantee
when an IPI will be received.

To fix this check for enqueued but not yet received IPIs in the
cpu_disable() path and call the respective handlers before the cpu
is marked offline.

Reported-by: Juergen Doelle <juergen.doelle@de.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Heiko Carstens 2013-05-22 10:24:37 +02:00 committed by Martin Schwidefsky
parent 576ebd7492
commit 9acf73b7d0
1 changed files with 20 additions and 25 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

45
arch/s390/kernel/smp.c
View File

@ -428,34 +428,27 @@ void smp_stop_cpu(void)
* This is the main routine where commands issued by other
* cpus are handled.
*/
static void smp_handle_ext_call(void)
{
unsigned long bits;
/* handle bit signal external calls */
bits = xchg(&pcpu_devices[smp_processor_id()].ec_mask, 0);
if (test_bit(ec_stop_cpu, &bits))
smp_stop_cpu();
if (test_bit(ec_schedule, &bits))
scheduler_ipi();
if (test_bit(ec_call_function, &bits))
generic_smp_call_function_interrupt();
if (test_bit(ec_call_function_single, &bits))
generic_smp_call_function_single_interrupt();
}
static void do_ext_call_interrupt(struct ext_code ext_code,
unsigned int param32, unsigned long param64)
{
unsigned long bits;
int cpu;
cpu = smp_processor_id();
if (ext_code.code == 0x1202)
inc_irq_stat(IRQEXT_EXC);
else
inc_irq_stat(IRQEXT_EMS);
/*
* handle bit signal external calls
*/
bits = xchg(&pcpu_devices[cpu].ec_mask, 0);
if (test_bit(ec_stop_cpu, &bits))
smp_stop_cpu();
if (test_bit(ec_schedule, &bits))
scheduler_ipi();
if (test_bit(ec_call_function, &bits))
generic_smp_call_function_interrupt();
if (test_bit(ec_call_function_single, &bits))
generic_smp_call_function_single_interrupt();
inc_irq_stat(ext_code.code == 0x1202 ? IRQEXT_EXC : IRQEXT_EMS);
smp_handle_ext_call();
}
void arch_send_call_function_ipi_mask(const struct cpumask *mask)
@ -760,6 +753,8 @@ int __cpu_disable(void)
{
unsigned long cregs[16];
/* Handle possible pending IPIs */
smp_handle_ext_call();
set_cpu_online(smp_processor_id(), false);
/* Disable pseudo page faults on this cpu. */
pfault_fini();