linux-kernel - [PATCH 4.1 258/267] ARM64: smp: Fix suspicious RCU usage with ipi tracepoints

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Date:	Fri, 31 Jul 2015 12:41:49 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, John Stultz <john.stultz@...aro.org>,
	Nicolas Pitre <nicolas.pitre@...aro.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Stephen Boyd <sboyd@...eaurora.org>,
	Catalin Marinas <catalin.marinas@....com>
Subject: [PATCH 4.1 258/267] ARM64: smp: Fix suspicious RCU usage with ipi tracepoints

4.1-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Stephen Boyd <sboyd@...eaurora.org>

commit be081d9bf3e163a9ed1ca2f0f14f08424c7f9016 upstream.

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@...aro.org>
Cc: Nicolas Pitre <nicolas.pitre@...aro.org>
Acked-by: Steven Rostedt <rostedt@...dmis.org>
Reviewed-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
Fixes: 45ed695ac10a ("ARM64: add IPI tracepoints")
Signed-off-by: Stephen Boyd <sboyd@...eaurora.org>
Signed-off-by: Catalin Marinas <catalin.marinas@....com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/arm64/kernel/smp.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -569,7 +569,7 @@ void handle_IPI(int ipinr, struct pt_reg
 	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]);
 	}

@@ -612,7 +612,7 @@ void handle_IPI(int ipinr, struct pt_reg
 	}

 	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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