linux-kernel - [PATCH 3.19.y-ckt 168/251] ARM64: smp: Fix suspicious RCU usage with ipi tracepoints

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Message-Id: <1437008972-9140-169-git-send-email-kamal@canonical.com>
Date:	Wed, 15 Jul 2015 18:08:09 -0700
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	John Stultz <john.stultz@...aro.org>,
	Nicolas Pitre <nicolas.pitre@...aro.org>,
	Stephen Boyd <sboyd@...eaurora.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 3.19.y-ckt 168/251] ARM64: smp: Fix suspicious RCU usage with ipi tracepoints

3.19.8-ckt4 -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: Kamal Mostafa <kamal@...onical.com>
---
 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 e1b857f..c132df4 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -570,7 +570,7 @@ 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]);
 	}
 
@@ -619,7 +619,7 @@ 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);
 }
 
-- 
1.9.1

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