Commit edf55fda authored Jul 11, 2012 by Frederic Weisbecker

x86: Exit RCU extended QS on notify resume



do_notify_resume() may be called on irq or exception
exit. But at that time the exception has already called
rcu_user_enter() and the irq has already called rcu_irq_exit().

Since it can use RCU read side critical section, we must call
rcu_user_exit() before doing anything there. Then we must call
back rcu_user_enter() after this function because we know we are
going to userspace from there.

This complete support for userspace RCU extended quiescent state
in x86-64.

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: Geoff Levand <geoff@infradead.org>
Cc: Gilad Ben Yossef <gilad@benyossef.com>
Cc: Hakan Akkan <hakanakkan@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Kevin Hilman <khilman@ti.com>
Cc: Max Krasnyansky <maxk@qualcomm.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: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

parent 0430499c

arch/x86/Kconfig

+1 −0

Original line number	Diff line number	Diff line
		@@ -97,6 +97,7 @@ config X86
		select KTIME_SCALAR if X86_32
		select GENERIC_STRNCPY_FROM_USER
		select GENERIC_STRNLEN_USER
		select HAVE_RCU_USER_QS if X86_64

		config INSTRUCTION_DECODER
		def_bool (KPROBES \|\| PERF_EVENTS \|\| UPROBES)

arch/x86/kernel/signal.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -779,6 +779,8 @@ static void do_signal(struct pt_regs *regs)
		void
		do_notify_resume(struct pt_regs regs, void unused, __u32 thread_info_flags)
		{
		rcu_user_exit();

		#ifdef CONFIG_X86_MCE
		/* notify userspace of pending MCEs */
		if (thread_info_flags & _TIF_MCE_NOTIFY)
		@@ -804,6 +806,8 @@ 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 */

		rcu_user_enter();
		}

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

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