Messages in this thread Patch in this message | | | From | Henrik Austad <> | Subject | [PATCH] tile: ns2cycles must be called with preempt disabled. | Date | Fri, 22 Mar 2013 18:37:51 +0100 |
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ns2cycles use per_cpu variables, and will, eventually, find its way into smp_processord_id(). The latter must be called with either preempt disabled, irq's off, from a thread locked to a single core or early in the bootprocess (according to debug_smp_processor_id())
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)
Note: wrapping the -entire- delay-loop in a preempt-off section can be a bad idea as long delays would case kernel lockups without being able to preempt the thread at all.
Signed-off-by: Henrik Austad <haustad@cisco.com> --- arch/tile/lib/delay.c | 2 ++ 1 files changed, 2 insertions(+), 0 deletions(-)
diff --git a/arch/tile/lib/delay.c b/arch/tile/lib/delay.c index cdacdd1..a53cdcd 100644 --- a/arch/tile/lib/delay.c +++ b/arch/tile/lib/delay.c @@ -30,7 +30,9 @@ EXPORT_SYMBOL(__udelay); void __ndelay(unsigned long nsecs) { cycles_t target = get_cycles(); + preempt_disable(); target += ns2cycles(nsecs); + preempt_enable(); while (get_cycles() < target) cpu_relax(); } -- 1.7.2.5
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