tile: ns2cycles should use __raw_get_cpu_var
ns2cycles use per_cpu variables, and will, eventually, find its way into
smp_processor_id(). This is not safe in a preemptible kernel;
preemption should ideally be disabled.
BUG: using smp_processor_id() in preemptible [00000000] code:
systemd-modules/367
caller is ns2cycles+0x40/0xb8
Starting stack dump of tid 367, pid 367 (systemd-modules) on cpu 2 at
cycle 20969956421
frame 0: 0xfffffff70004b860 dump_stack+0x0/0x20 (sp 0xfffffe407993fa90)
frame 1: 0xfffffff7006abc28 debug_smp_processor_id+0x1a8/0x1e0 (sp
0xfffffe407993fa90)
frame 2: 0xfffffff7004d7b40 ns2cycles+0x40/0xb8 (sp 0xfffffe407993fab8)
frame 3: 0xfffffff7004dc578 __ndelay+0x38/0x80 (sp 0xfffffe407993fae0)
However, in this case:
- the frequency is the same accross all cores
- we use the data read-only
- we do not scale the frequency
Which means that we can use the __raw_get_cpu_var instead.
Signed-off-by: Henrik Austad <haustad@cisco.com>
Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>
diff --git a/arch/tile/kernel/time.c b/arch/tile/kernel/time.c
index f6f50f2a..5ac397e 100644
--- a/arch/tile/kernel/time.c
+++ b/arch/tile/kernel/time.c
@@ -230,6 +230,10 @@
*/
cycles_t ns2cycles(unsigned long nsecs)
{
- struct clock_event_device *dev = &__get_cpu_var(tile_timer);
+ /*
+ * We do not have to disable preemption here as each core has the same
+ * clock frequency.
+ */
+ struct clock_event_device *dev = &__raw_get_cpu_var(tile_timer);
return ((u64)nsecs * dev->mult) >> dev->shift;
}