Blackfin: SMP: rewrite IPI handling to avoid memory allocation

Currently, sending an interprocessor interrupt (IPI) requires building up
a message dynamically which means memory allocation.  But often times, we
will want to send an IPI in low level contexts where allocation is not
possible which may lead to a panic().  So create a per-cpu static array
for the message queue and use that instead.

Further, while we have two supplemental interrupts, we are currently only
using one of them.  So use the second one for the most common IPI message
of all -- smp_send_reschedule().  This avoids ugly contention for locks
which in turn would require an IPI message ...

In general, this improves SMP performance, and in some cases allows the
SMP port to work in places it wouldn't before.  Such as the PREEMPT_RT
state where the slab is protected by a per-cpu spin lock.  If the slab
kmalloc/kfree were to put the task to sleep, and that task was actually
the IPI handler, then the system falls down yet again.

After running some various stress tests on the system, the static limit
of 5 messages seems to work.  On the off chance even this overflows, we
simply panic(), and we can review that scenario to see if the limit needs
to be increased a bit more.

Signed-off-by: Yi Li <yi.li@analog.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>

1 files changed, 15 insertions, 10 deletions

diff --git a/arch/blackfin/mach-bf561/smp.c b/arch/blackfin/mach-bf561/smp.c
index 1a19fad63f4..1074a7ef81c 100644
--- a/arch/blackfin/mach-bf561/smp.c
+++ b/arch/blackfin/mach-bf561/smp.c
@@ -111,41 +111,46 @@ int __cpuinit platform_boot_secondary(unsigned int cpu, struct task_struct *idle
 		panic("CPU%u: processor failed to boot\n", cpu);
 }
 
-void __init platform_request_ipi(void *handler)
+static const char supple0[] = "IRQ_SUPPLE_0";
+static const char supple1[] = "IRQ_SUPPLE_1";
+void __init platform_request_ipi(int irq, void *handler)
 {
 	int ret;
+	const char *name = (irq == IRQ_SUPPLE_0) ? supple0 : supple1;
 
-	ret = request_irq(IRQ_SUPPLE_0, handler, IRQF_DISABLED,
-			  "Supplemental Interrupt0", handler);
+	ret = request_irq(irq, handler, IRQF_DISABLED | IRQF_PERCPU, name, handler);
 	if (ret)
-		panic("Cannot request supplemental interrupt 0 for IPI service");
+		panic("Cannot request %s for IPI service", name);
 }
 
-void platform_send_ipi(cpumask_t callmap)
+void platform_send_ipi(cpumask_t callmap, int irq)
 {
 	unsigned int cpu;
+	int offset = (irq == IRQ_SUPPLE_0) ? 6 : 8;
 
 	for_each_cpu_mask(cpu, callmap) {
 		BUG_ON(cpu >= 2);
 		SSYNC();
-		bfin_write_SICB_SYSCR(bfin_read_SICB_SYSCR() | (1 << (6 + cpu)));
+		bfin_write_SICB_SYSCR(bfin_read_SICB_SYSCR() | (1 << (offset + cpu)));
 		SSYNC();
 	}
 }
 
-void platform_send_ipi_cpu(unsigned int cpu)
+void platform_send_ipi_cpu(unsigned int cpu, int irq)
 {
+	int offset = (irq == IRQ_SUPPLE_0) ? 6 : 8;
 	BUG_ON(cpu >= 2);
 	SSYNC();
-	bfin_write_SICB_SYSCR(bfin_read_SICB_SYSCR() | (1 << (6 + cpu)));
+	bfin_write_SICB_SYSCR(bfin_read_SICB_SYSCR() | (1 << (offset + cpu)));
 	SSYNC();
 }
 
-void platform_clear_ipi(unsigned int cpu)
+void platform_clear_ipi(unsigned int cpu, int irq)
 {
+	int offset = (irq == IRQ_SUPPLE_0) ? 10 : 12;
 	BUG_ON(cpu >= 2);
 	SSYNC();
-	bfin_write_SICB_SYSCR(bfin_read_SICB_SYSCR() | (1 << (10 + cpu)));
+	bfin_write_SICB_SYSCR(bfin_read_SICB_SYSCR() | (1 << (offset + cpu)));
 	SSYNC();
 }