From mboxrd@z Thu Jan 1 00:00:00 1970 From: paulmck@linux.vnet.ibm.com (Paul E. McKenney) Date: Wed, 24 Jun 2015 13:20:40 -0700 Subject: [PATCH] ARM64: smp: Silence suspicious RCU usage with ipi tracepoints In-Reply-To: <1435176858-9568-1-git-send-email-sboyd@codeaurora.org> References: <1435176858-9568-1-git-send-email-sboyd@codeaurora.org> Message-ID: <20150624202023.GK3717@linux.vnet.ibm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Wed, Jun 24, 2015 at 01:14:18PM -0700, Stephen Boyd wrote: > John Stultz reported an RCU splat on ARM with ipi trace events > enabled. It looks like the same problem exists on ARM64. > > At this point in the IPI handling path we haven't called > irq_enter() yet, so RCU doesn't know that we're about to exit > idle and properly warns that we're using RCU from an idle CPU. > Use trace_ipi_entry_rcuidle() instead of trace_ipi_entry() so > that RCU is informed about our exit from idle. > > Cc: John Stultz > Cc: Steven Rostedt > Cc: Paul E. McKenney > Cc: Nicolas Pitre > Fixes: 45ed695ac10a "ARM64: add IPI tracepoints" > Signed-off-by: Stephen Boyd Reviewed-by: Paul E. McKenney > --- > > I haven't confirmed this, but it looks an awful lot like the same > problem exists on ARM64. > > arch/arm64/kernel/smp.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c > index 4b2121bd7f9c..a1883bfdd9d6 100644 > --- a/arch/arm64/kernel/smp.c > +++ b/arch/arm64/kernel/smp.c > @@ -693,7 +693,7 @@ void handle_IPI(int ipinr, struct pt_regs *regs) > struct pt_regs *old_regs = set_irq_regs(regs); > > if ((unsigned)ipinr < NR_IPI) { > - trace_ipi_entry(ipi_types[ipinr]); > + trace_ipi_entry_rcuidle(ipi_types[ipinr]); > __inc_irq_stat(cpu, ipi_irqs[ipinr]); > } > > @@ -736,7 +736,7 @@ void handle_IPI(int ipinr, struct pt_regs *regs) > } > > if ((unsigned)ipinr < NR_IPI) > - trace_ipi_exit(ipi_types[ipinr]); > + trace_ipi_exit_rcuidle(ipi_types[ipinr]); > set_irq_regs(old_regs); > } > > -- > The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, > a Linux Foundation Collaborative Project >