The ia64_mca_cpe_int_handler() in 2.6.24 goes something like this:
ia64_mca_cpe_int_handler (int cpe_irq, void *arg)
{
...
/* SAL spec states this should run w/ interrupts enabled */
local_irq_enable();
spin_lock(&cpe_history_lock);
...
spin_unlock(&cpe_history_lock);
ia64_mca_log_sal_error_record(SAL_INFO_TYPE_CPE);
}
I think the interrupts are enabled too early. I just have caught a dead lock:
I have got nested ia64_mca_cpe_int_handler()-s, the first instance has
been interrupted somewhere between spin_lock(&cpe_history_lock) and
spin_unlock(&cpe_history_lock). Obviously, the second instance will never get
the lock.
The previous versions, e.g. 2.6.18, were not safe either:
ia64_mca_cpe_int_handler (int cpe_irq, void *arg, struct pt_regs *ptregs)
{
...
/* SAL spec states this should run w/ interrupts enabled */
local_irq_enable();
/* Get the CPE error record and log it */
ia64_mca_log_sal_error_record(SAL_INFO_TYPE_CPE);
spin_lock(&cpe_history_lock);
...
spin_unlock(&cpe_history_lock);
}
I think the interrupts have to be blocked while we are inside the lock-
protected region.
I can think of something like this below. Please have a look at this patch.
Thanks,
Zoltan Menyhart
--- linux-2.6.24-old/arch/ia64/kernel/mca.c 2008-02-22 18:09:12.000000000
+0100
+++ linux-2.6.24/arch/ia64/kernel/mca.c 2008-02-22 18:09:26.000000000 +0100
@@ -436,6 +436,10 @@
static const char * const rec_name[] = { "MCA", "INIT", "CMC", "CPE" };
#endif
+ if (irq_safe){
+ /* SAL spec states this should run w/ interrupts enabled */
+ local_irq_enable();
+ }
size = ia64_log_get(sal_info_type, &buffer, irq_safe);
if (!size)
return;
@@ -512,9 +516,6 @@
IA64_MCA_DEBUG("%s: received interrupt vector = %#x on CPU %d\n",
__FUNCTION__, cpe_irq, smp_processor_id());
- /* SAL spec states this should run w/ interrupts enabled */
- local_irq_enable();
-
spin_lock(&cpe_history_lock);
if (!cpe_poll_enabled && cpe_vector >= 0) {
@@ -1324,9 +1325,6 @@
IA64_MCA_DEBUG("%s: received interrupt vector = %#x on CPU %d\n",
__FUNCTION__, cmc_irq, smp_processor_id());
- /* SAL spec states this should run w/ interrupts enabled */
- local_irq_enable();
-
spin_lock(&cmc_history_lock);
if (!cmc_polling_enabled) {
int i, count = 1; /* we know 1 happened now */
