Date:	Fri, 27 Jul 2012 17:40:30 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	LKML <linux-kernel@...r.kernel.org>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	Alessio Igor Bogani <abogani@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Avi Kivity <avi@...hat.com>,
	Chris Metcalf <cmetcalf@...era.com>,
	Christoph Lameter <cl@...ux.com>,
	Geoff Levand <geoff@...radead.org>,
	Gilad Ben Yossef <gilad@...yossef.com>,
	Hakan Akkan <hakanakkan@...il.com>,
	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...nel.org>,
	Kevin Hilman <khilman@...com>,
	Max Krasnyansky <maxk@...lcomm.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Stephen Hemminger <shemminger@...tta.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Sven-Thorsten Dietrich <thebigcorporation@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH 1/5] user_hooks: New user hooks subsystem

Create a new subsystem that handles the hooks on kernel/user
boundaries currently used by RCU for its userspace extended
quiescent state.

We need to pull this up from RCU into this new level of indirection
because these hooks are also going to be used to implement an "on
demand" generic virtual cputime accounting. A necessary step to
shutdown the tick while still accounting the cputime.

Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
Cc: Alessio Igor Bogani <abogani@...nel.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Avi Kivity <avi@...hat.com>
Cc: Chris Metcalf <cmetcalf@...era.com>
Cc: Christoph Lameter <cl@...ux.com>
Cc: Geoff Levand <geoff@...radead.org>
Cc: Gilad Ben Yossef <gilad@...yossef.com>
Cc: Hakan Akkan <hakanakkan@...il.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Kevin Hilman <khilman@...com>
Cc: Max Krasnyansky <maxk@...lcomm.com>
Cc: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Stephen Hemminger <shemminger@...tta.com>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Sven-Thorsten Dietrich <thebigcorporation@...il.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
---
 arch/Kconfig                                 |   10 ++--
 arch/x86/Kconfig                             |    2 +-
 arch/x86/include/asm/{rcu.h => user_hooks.h} |   12 +++---
 arch/x86/kernel/ptrace.c                     |    6 +-
 arch/x86/kernel/signal.c                     |    5 +-
 arch/x86/kernel/traps.c                      |    2 +-
 arch/x86/mm/fault.c                          |    2 +-
 include/linux/rcupdate.h                     |    2 -
 include/linux/sched.h                        |    8 ----
 include/linux/user_hooks.h                   |   18 ++++++++
 init/Kconfig                                 |   24 +++++++----
 kernel/Makefile                              |    1 +
 kernel/rcutree.c                             |   42 +------------------
 kernel/sched/core.c                          |    9 ++--
 kernel/user_hooks.c                          |   56 ++++++++++++++++++++++++++
 15 files changed, 117 insertions(+), 82 deletions(-)
 rename arch/x86/include/asm/{rcu.h => user_hooks.h} (56%)
 create mode 100644 include/linux/user_hooks.h
 create mode 100644 kernel/user_hooks.c

diff --git a/arch/Kconfig b/arch/Kconfig
index d891c62..b8b987c 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -277,14 +277,14 @@ config SECCOMP_FILTER
 config HAVE_VIRT_CPU_ACCOUNTING
 	bool
 
-config HAVE_RCU_USER_QS
+config HAVE_USER_HOOKS
 	bool
 	help
 	  Provide kernel entry/exit hooks necessary for userspace
 	  RCU extended quiescent state. Syscalls need to be wrapped inside
-	  rcu_user_exit()-rcu_user_enter() through the slow path using
-	  TIF_NOHZ flag. Exceptions handlers must be wrapped as well. Irqs
-	  are already protected inside rcu_irq_enter/rcu_irq_exit() but
-	  preemption or signal handling on irq exit still need to be protected.
+	  user_exit()-user_enter() through the slow path using TIF_NOHZ flag.
+	  Exceptions handlers must be wrapped as well. Irqs are already
+	  protected inside rcu_irq_enter/rcu_irq_exit() but preemption or
+	  signal handling on irq exit still need to be protected.
 
 source "kernel/gcov/Kconfig"
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 38dfcc2..ee2ca37 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -95,7 +95,7 @@ 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
+	select HAVE_USER_HOOKS if X86_64
 
 config INSTRUCTION_DECODER
 	def_bool (KPROBES || PERF_EVENTS || UPROBES)
diff --git a/arch/x86/include/asm/rcu.h b/arch/x86/include/asm/user_hooks.h
similarity index 56%
rename from arch/x86/include/asm/rcu.h
rename to arch/x86/include/asm/user_hooks.h
index 439815b..b5d10ef 100644
--- a/arch/x86/include/asm/rcu.h
+++ b/arch/x86/include/asm/user_hooks.h
@@ -1,19 +1,19 @@
-#ifndef _ASM_X86_RCU_H
-#define _ASM_X86_RCU_H
+#ifndef _ASM_X86_USER_HOOKS_H
+#define _ASM_X86_USER_HOOKS_H
 
-#include <linux/rcupdate.h>
+#include <linux/user_hooks.h>
 #include <asm/ptrace.h>
 
 static inline void exception_enter(struct pt_regs *regs)
 {
-	rcu_user_exit();
+	user_exit();
 }
 
 static inline void exception_exit(struct pt_regs *regs)
 {
-#ifdef CONFIG_RCU_USER_QS
+#ifdef CONFIG_USER_HOOKS
 	if (user_mode(regs))
-		rcu_user_enter();
+		user_enter();
 #endif
 }
 
diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
index 9f94f8e..a8137b3 100644
--- a/arch/x86/kernel/ptrace.c
+++ b/arch/x86/kernel/ptrace.c
@@ -21,7 +21,7 @@
 #include <linux/signal.h>
 #include <linux/perf_event.h>
 #include <linux/hw_breakpoint.h>
-#include <linux/rcupdate.h>
+#include <linux/user_hooks.h>
 
 #include <asm/uaccess.h>
 #include <asm/pgtable.h>
@@ -1464,7 +1464,7 @@ long syscall_trace_enter(struct pt_regs *regs)
 {
 	long ret = 0;
 
-	rcu_user_exit();
+	user_exit();
 
 	/*
 	 * If we stepped into a sysenter/syscall insn, it trapped in
@@ -1530,5 +1530,5 @@ void syscall_trace_leave(struct pt_regs *regs)
 	if (step || test_thread_flag(TIF_SYSCALL_TRACE))
 		tracehook_report_syscall_exit(regs, step);
 
-	rcu_user_enter();
+	user_enter();
 }
diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
index 5cc2579..61edb6b 100644
--- a/arch/x86/kernel/signal.c
+++ b/arch/x86/kernel/signal.c
@@ -19,6 +19,7 @@
 #include <linux/uaccess.h>
 #include <linux/user-return-notifier.h>
 #include <linux/uprobes.h>
+#include <linux/user_hooks.h>
 
 #include <asm/processor.h>
 #include <asm/ucontext.h>
@@ -776,7 +777,7 @@ 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();
+	user_exit();
 
 #ifdef CONFIG_X86_MCE
 	/* notify userspace of pending MCEs */
@@ -804,7 +805,7 @@ do_notify_resume(struct pt_regs *regs, void *unused, __u32 thread_info_flags)
 	clear_thread_flag(TIF_IRET);
 #endif /* CONFIG_X86_32 */
 
-	rcu_user_enter();
+	user_enter();
 }
 
 void signal_fault(struct pt_regs *regs, void __user *frame, char *where)
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 9b8195b..f563a07 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -52,7 +52,7 @@
 #include <asm/i387.h>
 #include <asm/fpu-internal.h>
 #include <asm/mce.h>
-#include <asm/rcu.h>
+#include <asm/user_hooks.h>
 
 #include <asm/mach_traps.h>
 
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 7dde46d..1906366 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -18,7 +18,7 @@
 #include <asm/pgalloc.h>		/* pgd_*(), ...			*/
 #include <asm/kmemcheck.h>		/* kmemcheck_*(), ...		*/
 #include <asm/fixmap.h>			/* VSYSCALL_START		*/
-#include <asm/rcu.h>			/* exception_enter(), ...	*/
+#include <asm/user_hooks.h>		/* exception_enter(), ...	*/
 
 /*
  * Page fault error code bits:
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 1fc0a0e..e411117 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -197,8 +197,6 @@ extern void rcu_user_enter(void);
 extern void rcu_user_exit(void);
 extern void rcu_user_enter_irq(void);
 extern void rcu_user_exit_irq(void);
-extern void rcu_user_hooks_switch(struct task_struct *prev,
-				  struct task_struct *next);
 #else
 static inline void rcu_user_enter(void) { }
 static inline void rcu_user_exit(void) { }
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 30105f4..7b7a438 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1899,14 +1899,6 @@ static inline void rcu_copy_process(struct task_struct *p)
 
 #endif
 
-static inline void rcu_switch(struct task_struct *prev,
-			      struct task_struct *next)
-{
-#ifdef CONFIG_RCU_USER_QS
-	rcu_user_hooks_switch(prev, next);
-#endif
-}
-
 #ifdef CONFIG_SMP
 extern void do_set_cpus_allowed(struct task_struct *p,
 			       const struct cpumask *new_mask);
diff --git a/include/linux/user_hooks.h b/include/linux/user_hooks.h
new file mode 100644
index 0000000..720292d
--- /dev/null
+++ b/include/linux/user_hooks.h
@@ -0,0 +1,18 @@
+#ifndef _LINUX_USER_HOOKS_H
+#define _LINUX_USER_HOOKS_H
+
+#ifdef CONFIG_USER_HOOKS
+#include <linux/sched.h>
+
+extern void user_enter(void);
+extern void user_exit(void);
+extern void user_hooks_switch(struct task_struct *prev,
+			      struct task_struct *next);
+#else
+static inline void user_enter(void) { }
+static inline void user_exit(void) { }
+static inline void user_hooks_switch(struct task_struct *prev,
+				     struct task_struct *next) { }
+#endif /* !CONFIG_USER_HOOKS */
+
+#endif
diff --git a/init/Kconfig b/init/Kconfig
index cc1d581..3348b85 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -404,6 +404,19 @@ config AUDIT_LOGINUID_IMMUTABLE
 source "kernel/irq/Kconfig"
 source "kernel/time/Kconfig"
 
+config USER_HOOKS
+       bool
+
+config USER_HOOKS_FORCE
+	bool "Force userspace hooks"
+	depends on USER_HOOKS
+	help
+	  Set the hooks in user/kernel boundaries by default in order to
+	  test the features that rely on it such as userspace RCU extended
+	  quiescent states.
+	  This test is there for debugging until we have a real user like a
+	  full adaptive nohz option.
+
 menu "RCU Subsystem"
 
 choice
@@ -456,7 +469,8 @@ config PREEMPT_RCU
 
 config RCU_USER_QS
 	bool "Consider userspace as in RCU extended quiescent state"
-	depends on HAVE_RCU_USER_QS && SMP
+	depends on HAVE_USER_HOOKS && SMP
+	select USER_HOOKS
 	help
 	  This option sets hooks on kernel / userspace boundaries and
 	  puts RCU in extended quiescent state when the CPU runs in
@@ -464,14 +478,6 @@ config RCU_USER_QS
 	  excluded from the global RCU state machine and thus doesn't
 	  to keep the timer tick on for RCU.
 
-config RCU_USER_QS_FORCE
-	bool "Force userspace extended QS by default"
-	depends on RCU_USER_QS
-	help
-	  Set the hooks in user/kernel boundaries by default in order to
-	  test this feature that treats userspace as an extended quiescent
-	  state until we have a real user like a full adaptive nohz option.
-
 config RCU_FANOUT
 	int "Tree-based hierarchical RCU fanout value"
 	range 2 64 if 64BIT
diff --git a/kernel/Makefile b/kernel/Makefile
index c0cc67a..78d2c1e 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -110,6 +110,7 @@ obj-$(CONFIG_USER_RETURN_NOTIFIER) += user-return-notifier.o
 obj-$(CONFIG_PADATA) += padata.o
 obj-$(CONFIG_CRASH_DUMP) += crash_dump.o
 obj-$(CONFIG_JUMP_LABEL) += jump_label.o
+obj-$(CONFIG_USER_HOOKS) += user_hooks.o
 
 $(obj)/configs.o: $(obj)/config_data.h
 
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 318d00e..f6a24cb 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -212,9 +212,6 @@ EXPORT_SYMBOL_GPL(rcu_note_context_switch);
 DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = {
 	.dynticks_nesting = DYNTICK_TASK_EXIT_IDLE,
 	.dynticks = ATOMIC_INIT(1),
-#if defined(CONFIG_RCU_USER_QS) && !defined(CONFIG_RCU_USER_QS_FORCE)
-	.ignore_user_qs = true,
-#endif
 };
 
 static int blimit = 10;		/* Maximum callbacks per rcu_do_batch. */
@@ -448,18 +445,7 @@ EXPORT_SYMBOL_GPL(rcu_idle_enter);
  */
 void rcu_user_enter(void)
 {
-	unsigned long flags;
-	struct rcu_dynticks *rdtp;
-
-	WARN_ON_ONCE(!current->mm);
-
-	local_irq_save(flags);
-	rdtp = &__get_cpu_var(rcu_dynticks);
-	if (!rdtp->ignore_user_qs && !rdtp->in_user) {
-		rdtp->in_user = true;
-		rcu_eqs_enter(1);
-	}
-	local_irq_restore(flags);
+	rcu_eqs_enter(1);
 }
 EXPORT_SYMBOL_GPL(rcu_user_enter);
 
@@ -597,16 +583,7 @@ EXPORT_SYMBOL_GPL(rcu_idle_exit);
  */
 void rcu_user_exit(void)
 {
-	unsigned long flags;
-	struct rcu_dynticks *rdtp;
-
-	local_irq_save(flags);
-	rdtp = &__get_cpu_var(rcu_dynticks);
-	if (rdtp->in_user) {
-		rdtp->in_user = false;
-		rcu_eqs_exit(1);
-	}
-	local_irq_restore(flags);
+	rcu_eqs_exit(1);
 }
 EXPORT_SYMBOL_GPL(rcu_user_exit);
 
@@ -730,21 +707,6 @@ int rcu_is_cpu_idle(void)
 }
 EXPORT_SYMBOL(rcu_is_cpu_idle);
 
-#ifdef CONFIG_RCU_USER_QS
-void rcu_user_hooks_switch(struct task_struct *prev,
-			   struct task_struct *next)
-{
-	struct rcu_dynticks *rdtp;
-
-	/* Interrupts are disabled in context switch */
-	rdtp = &__get_cpu_var(rcu_dynticks);
-	if (!rdtp->ignore_user_qs) {
-		clear_tsk_thread_flag(prev, TIF_NOHZ);
-		set_tsk_thread_flag(next, TIF_NOHZ);
-	}
-}
-#endif /* #ifdef CONFIG_RCU_USER_QS */
-
 #if defined(CONFIG_PROVE_RCU) && defined(CONFIG_HOTPLUG_CPU)
 
 /*
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 94a4894..fd7525b 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -72,6 +72,7 @@
 #include <linux/slab.h>
 #include <linux/init_task.h>
 #include <linux/binfmts.h>
+#include <linux/user_hooks.h>
 
 #include <asm/switch_to.h>
 #include <asm/tlb.h>
@@ -1926,7 +1927,7 @@ context_switch(struct rq *rq, struct task_struct *prev,
 #endif
 
 	/* Here we just switch the register state and the stack. */
-	rcu_switch(prev, next);
+	user_hooks_switch(prev, next);
 	switch_to(prev, next, prev);
 
 	barrier();
@@ -2920,9 +2921,9 @@ EXPORT_SYMBOL(schedule);
 
 asmlinkage void __sched schedule_user(void)
 {
-	rcu_user_exit();
+	user_exit();
 	schedule();
-	rcu_user_enter();
+	user_enter();
 }
 
 /**
@@ -3026,7 +3027,7 @@ asmlinkage void __sched preempt_schedule_irq(void)
 	/* Catch callers which need to be fixed */
 	BUG_ON(ti->preempt_count || !irqs_disabled());
 
-	rcu_user_exit();
+	user_exit();
 	do {
 		add_preempt_count(PREEMPT_ACTIVE);
 		local_irq_enable();
diff --git a/kernel/user_hooks.c b/kernel/user_hooks.c
new file mode 100644
index 0000000..63174b0
--- /dev/null
+++ b/kernel/user_hooks.c
@@ -0,0 +1,56 @@
+#include <linux/user_hooks.h>
+#include <linux/rcupdate.h>
+#include <linux/sched.h>
+#include <linux/percpu.h>
+
+struct user_hooks {
+	bool hooking;
+	bool in_user;
+};
+
+DEFINE_PER_CPU(struct user_hooks, user_hooks) = {
+#ifdef CONFIG_USER_HOOKS_FORCE
+	.hooking = true,
+#endif
+};
+
+void user_enter(void)
+{
+	unsigned long flags;
+	struct user_hooks *uh;
+
+	WARN_ON_ONCE(!current->mm);
+	local_irq_save(flags);
+	uh = &__get_cpu_var(user_hooks);
+	if (uh->hooking && !uh->in_user) {
+		uh->in_user = true;
+		rcu_user_enter();
+	}
+	local_irq_restore(flags);
+}
+
+void user_exit(void)
+{
+	unsigned long flags;
+	struct user_hooks *uh;
+
+	local_irq_save(flags);
+	uh = &__get_cpu_var(user_hooks);
+	if (uh->in_user) {
+		uh->in_user = false;
+		rcu_user_exit();
+	}
+	local_irq_restore(flags);
+}
+
+void user_hooks_switch(struct task_struct *prev,
+		       struct task_struct *next)
+{
+	struct user_hooks *uh;
+
+	uh = &__get_cpu_var(user_hooks);
+	if (uh->hooking) {
+		clear_tsk_thread_flag(prev, TIF_NOHZ);
+		set_tsk_thread_flag(next, TIF_NOHZ);
+	}
+}
-- 
1.7.5.4

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Powered by blists - more mailing lists