Messages in this thread | | | From | Joel Fernandes <> | Date | Thu, 20 Oct 2022 10:52:04 -0400 | Subject | Re: [PATCH] tracing: Add trace_trigger kernel command line option |
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On Thu, Oct 20, 2022 at 10:43 AM Joel Fernandes <joel@joelfernandes.org> wrote: > > Hi Steven, > > On Wed, Oct 19, 2022 at 8:01 PM Steven Rostedt <rostedt@goodmis.org> wrote: > > > > From: "Steven Rostedt (Google)" <rostedt@goodmis.org> > > > > Allow triggers to be enabled at kernel boot up. For example: > > > > trace_trigger="sched_switch.stacktrace if prev_state == 2" > > > > The above will enable the stacktrace trigger on top of the sched_switch > > event and only trigger if its prev_state is 2 (TASK_UNINTERRUPTIBLE). Then > > at boot up, a stacktrace will trigger and be recorded in the tracing ring > > buffer every time the sched_switch happens where the previous state is > > TASK_INTERRUPTIBLE. > > > > As this calls into tracepoint logic during very early boot (before > > interrupts are enabled), a check has to be done to see if early boot > > interrupts are still disabled, and if so, avoid any call to RCU > > synchronization, as that will enable interrupts and cause boot up issues. > > > > Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> > > --- > > rest_init() -> rcu_scheduler_starting() sets RCU_SCHEDULER_INIT > > start_kernel() disables interrupts and does the dance you mentioned, > while setting that early_ flag. start_kernel() is called from arch > code. > > From your crash, the trace trigger is happening before the early_ boot > flag is set to true.
My apologies. I meant, before early_boot_irqs_disabled is set to false.
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