Messages in this thread | | | From | "Rafael J. Wysocki" <> | Date | Thu, 25 Aug 2022 13:43:57 +0200 | Subject | Re: [PATCH v2] intel_idle: avoid tracing MSR writes while idling |
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On Thu, Aug 25, 2022 at 1:42 AM Peter Shier <pshier@google.com> wrote: > > With commit bf5835bcdb963 ("intel_idle: Disable IBRS during long idle"), > enabling wrmsr trace with CONFIG_LOCKDEP causes "suspicious > rcu_dereference_check() usage" warning because do_trace_write_msr does not > use trace_write_msr_rcuidle. > > Change intel_idle_ibrs to use native_wrmsr to avoid tracing > > Sample warning: > ============================ > WARNING: suspicious RCU usage > 6.0.0-dbg-DEV #7 Tainted: G S O > ----------------------------- > arch/x86/include/asm/msr-trace.h:48 suspicious rcu_dereference_check() usage! > > other info that might help us debug this: > > rcu_scheduler_active = 2, debug_locks = 1 > RCU used illegally from extended quiescent state! > no locks held by swapper/59/0. > > stack backtrace: > CPU: 59 PID: 0 Comm: swapper/59 Tainted: G S O 6.0.0-dbg-DEV #7 > Call Trace: > dump_stack_lvl > dump_stack > lockdep_rcu_suspicious > trace_write_msr > do_trace_write_msr > intel_idle_ibrs > cpuidle_enter_state > cpuidle_enter > do_idle > cpu_startup_entry > start_secondary > secondary_startup_64_no_verify > > Tested on skylake using: > echo "msr:write_msr" >/sys/kernel/debug/tracing/set_event > with and without patch. > > Signed-off-by: Peter Shier <pshier@google.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> --- > > v2: > - changed to avoid tracing > > v1: https://lore.kernel.org/all/20220823234353.937002-1-pshier@google.com/ > > drivers/idle/intel_idle.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c > index 3e101719689a..df129c73786f 100644 > --- a/drivers/idle/intel_idle.c > +++ b/drivers/idle/intel_idle.c > @@ -187,12 +187,12 @@ static __cpuidle int intel_idle_ibrs(struct cpuidle_device *dev, > int ret; > > if (smt_active) > - wrmsrl(MSR_IA32_SPEC_CTRL, 0); > + native_wrmsr(MSR_IA32_SPEC_CTRL, 0); > > ret = __intel_idle(dev, drv, index); > > if (smt_active) > - wrmsrl(MSR_IA32_SPEC_CTRL, spec_ctrl); > + native_wrmsr(MSR_IA32_SPEC_CTRL, spec_ctrl); > > return ret; > } > --
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