Commit be081d9b authored Jun 24, 2015 by Stephen Boyd Committed by Catalin Marinas Jun 25, 2015

ARM64: smp: Fix suspicious RCU usage with ipi tracepoints



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 <john.stultz@linaro.org>
Cc: Nicolas Pitre <nicolas.pitre@linaro.org>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: <stable@vger.kernel.org> # 3.17+
Fixes: 45ed695a ("ARM64: add IPI tracepoints")
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

parent 86dca36e

arch/arm64/kernel/smp.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -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);
		}

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