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Subject[PATCH 26/32] x86: Add adaptive tickless hooks on do_notify_resume()
Date
Before resuming to userspace, we may fall into do_notify_resume()
to handle signals or other things. And because we may be coming
from syscall/exception or interrupt exit, we may be running into
RCU idle mode as we resume tickless to userspace.

However do_notify_resume() may make use of RCU read side critical
sections so we need to exit RCU idle mode before doing anything in
that path.

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: Ingo Molnar <mingo@kernel.org>
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>
Cc: Zen Lin <zen@openhuawei.org>
---
arch/x86/kernel/signal.c | 3 +++
1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
index 46a01bd..577fd93 100644
--- a/arch/x86/kernel/signal.c
+++ b/arch/x86/kernel/signal.c
@@ -20,6 +20,7 @@
#include <linux/personality.h>
#include <linux/uaccess.h>
#include <linux/user-return-notifier.h>
+#include <linux/tick.h>

#include <asm/processor.h>
#include <asm/ucontext.h>
@@ -810,6 +811,7 @@ static void do_signal(struct pt_regs *regs)
void
do_notify_resume(struct pt_regs *regs, void *unused, __u32 thread_info_flags)
{
+ tick_nohz_enter_kernel();
#ifdef CONFIG_X86_MCE
/* notify userspace of pending MCEs */
if (thread_info_flags & _TIF_MCE_NOTIFY)
@@ -832,6 +834,7 @@ do_notify_resume(struct pt_regs *regs, void *unused, __u32 thread_info_flags)
#ifdef CONFIG_X86_32
clear_thread_flag(TIF_IRET);
#endif /* CONFIG_X86_32 */
+ tick_nohz_exit_kernel();
}

void signal_fault(struct pt_regs *regs, void __user *frame, char *where)
--
1.7.5.4


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