* Frederic Weisbecker <fweisbec@xxxxxxxxx> wrote: > > > It seems to run fine for all of them except sysprof. It passes the self-test > > > but doesn't produce any trace when I manually try. > > > > > > Not completely sure this is only in -rt so I'm pulling very latest -tip and > > > will see if I find the same problem there. > > > > About sysprof, it's an -rt problem, I don't see it on -tip. The sysprof hrtimer > > callback is never called. > > > > I'm digging to see what is happening. > > I didn't put my ftrace_printk at the right place. It doesn't come from hrtimer. > The problem comes from get_irq_regs() which always returns NULL on the sysprof > hrtimer calback, then the trace is immediately dropped by sysprof. Ah, that makes sense - under -rt the default hrtimer execution is to execute in a softirq context. Could you try the patch below please, does it fix sysprof? Ingo ------------------> Subject: rt: sysprof hrtimer fix From: Ingo Molnar <mingo@xxxxxxx> Date: Fri Feb 13 08:22:14 CET 2009 Frederic Weisbecker noticed that sysprof does not work under .29-rt2, and tracked it down to a NULL result that get_irq_regs() gives to the sysprof plugin. The reason for the NULL is that it executes in the HRTIMER_SOFTIRQ context, hence it does not interrupt any real context and thus there's no IRQ registers to take a look at. Since the sysprof functionality is atomic, the fix is to move the sysprof hrtimers to hardirq context. Reported-by: Frederic Weisbecker <fweisbec@xxxxxxxxx> Signed-off-by: Ingo Molnar <mingo@xxxxxxx> --- kernel/trace/trace_sysprof.c | 1 + 1 file changed, 1 insertion(+) Index: tip/kernel/trace/trace_sysprof.c =================================================================== --- tip.orig/kernel/trace/trace_sysprof.c +++ tip/kernel/trace/trace_sysprof.c @@ -202,6 +202,7 @@ static void start_stack_timer(void *unus hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); hrtimer->function = stack_trace_timer_fn; + hrtimer->irqsafe = 1; hrtimer_start(hrtimer, ns_to_ktime(sample_period), HRTIMER_MODE_REL); } -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
