ns2cycles use per_cpu variables, and will, eventually, find its way into smp_processord_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 <[email protected]> --- arch/tile/kernel/time.c | 6 +++++- 1 files changed, 5 insertions(+), 1 deletions(-) diff --git a/arch/tile/kernel/time.c b/arch/tile/kernel/time.c index 42297f6..1dc1d61 100644 --- a/arch/tile/kernel/time.c +++ b/arch/tile/kernel/time.c @@ -234,7 +234,11 @@ int setup_profiling_timer(unsigned int multiplier) */ cycles_t ns2cycles(unsigned long nsecs) { - struct clock_event_device *dev = &__get_cpu_var(tile_timer); + /* + * We do not have to disable preemptions 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; } -- 1.7.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
