From: Frederic Weisbecker <fweisbec@gmail.com>

Add syscall hooks to notify syscall entry and exit on
CPUs running in adative nohz mode.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Alessio Igor Bogani <abogani@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Avi Kivity <avi@redhat.com>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Geoff Levand <geoff@infradead.org>
Cc: Gilad Ben Yossef <gilad@benyossef.com>
Cc: Hakan Akkan <hakanakkan@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Kevin Hilman <khilman@ti.com>
Cc: Max Krasnyansky <maxk@qualcomm.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Hemminger <shemminger@vyatta.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Sven-Thorsten Dietrich <thebigcorporation@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 arch/x86/kernel/ptrace.c |   11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
index b00b33a..9c18e1e 100644
--- a/arch/x86/kernel/ptrace.c
+++ b/arch/x86/kernel/ptrace.c
@@ -22,6 +22,7 @@
 #include <linux/perf_event.h>
 #include <linux/hw_breakpoint.h>
 #include <linux/rcupdate.h>
+#include <linux/tick.h>
 
 #include <asm/uaccess.h>
 #include <asm/pgtable.h>
@@ -1461,6 +1462,10 @@ long syscall_trace_enter(struct pt_regs *regs)
 {
 	long ret = 0;
 
+	/* Notify nohz task syscall early so the rest can use rcu */
+	/* (SDR: Does the rcu_user_exit() make this obsolete?) */
+	tick_nohz_enter_kernel();
+
 	rcu_user_exit();
 
 	/*
@@ -1528,4 +1533,10 @@ void syscall_trace_leave(struct pt_regs *regs)
 		tracehook_report_syscall_exit(regs, step);
 
 	rcu_user_enter();
+	/*
+	 * Notify nohz task exit syscall at last so the rest can
+	 * use rcu.
+	 * (SDR: does the above make this obsolete?)
+	 */
+	tick_nohz_exit_kernel();
 }
-- 
1.7.10.4


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