Merge branch 'WIP.locking/seqlocks' into locking/urgent

Pick up the full seqlock series PeterZ is working on.

Signed-off-by: Ingo Molnar <mingo@kernel.org>

7 files changed, 102 insertions, 63 deletions

diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c
index f09288431f28..54ad1890aefc 100644
--- a/arch/x86/entry/common.c
+++ b/arch/x86/entry/common.c
@@ -559,8 +559,7 @@ SYSCALL_DEFINE0(ni_syscall)
 }
 
 /**
- * idtentry_enter_cond_rcu - Handle state tracking on idtentry with conditional
- *			     RCU handling
+ * idtentry_enter - Handle state tracking on ordinary idtentries
  * @regs:	Pointer to pt_regs of interrupted context
  *
  * Invokes:
@@ -572,6 +571,9 @@ SYSCALL_DEFINE0(ni_syscall)
  *  - The hardirq tracer to keep the state consistent as low level ASM
  *    entry disabled interrupts.
  *
+ * As a precondition, this requires that the entry came from user mode,
+ * idle, or a kernel context in which RCU is watching.
+ *
  * For kernel mode entries RCU handling is done conditional. If RCU is
  * watching then the only RCU requirement is to check whether the tick has
  * to be restarted. If RCU is not watching then rcu_irq_enter() has to be
@@ -585,18 +587,21 @@ SYSCALL_DEFINE0(ni_syscall)
  * establish the proper context for NOHZ_FULL. Otherwise scheduling on exit
  * would not be possible.
  *
- * Returns: True if RCU has been adjusted on a kernel entry
- *	    False otherwise
+ * Returns: An opaque object that must be passed to idtentry_exit()
  *
- * The return value must be fed into the rcu_exit argument of
- * idtentry_exit_cond_rcu().
+ * The return value must be fed into the state argument of
+ * idtentry_exit().
  */
-bool noinstr idtentry_enter_cond_rcu(struct pt_regs *regs)
+noinstr idtentry_state_t idtentry_enter(struct pt_regs *regs)
 {
+	idtentry_state_t ret = {
+		.exit_rcu = false,
+	};
+
 	if (user_mode(regs)) {
 		check_user_regs(regs);
 		enter_from_user_mode();
-		return false;
+		return ret;
 	}
 
 	/*
@@ -634,7 +639,8 @@ bool noinstr idtentry_enter_cond_rcu(struct pt_regs *regs)
 		trace_hardirqs_off_finish();
 		instrumentation_end();
 
-		return true;
+		ret.exit_rcu = true;
+		return ret;
 	}
 
 	/*
@@ -649,7 +655,7 @@ bool noinstr idtentry_enter_cond_rcu(struct pt_regs *regs)
 	trace_hardirqs_off();
 	instrumentation_end();
 
-	return false;
+	return ret;
 }
 
 static void idtentry_exit_cond_resched(struct pt_regs *regs, bool may_sched)
@@ -667,10 +673,9 @@ static void idtentry_exit_cond_resched(struct pt_regs *regs, bool may_sched)
 }
 
 /**
- * idtentry_exit_cond_rcu - Handle return from exception with conditional RCU
- *			    handling
+ * idtentry_exit - Handle return from exception that used idtentry_enter()
  * @regs:	Pointer to pt_regs (exception entry regs)
- * @rcu_exit:	Invoke rcu_irq_exit() if true
+ * @state:	Return value from matching call to idtentry_enter()
  *
  * Depending on the return target (kernel/user) this runs the necessary
  * preemption and work checks if possible and reguired and returns to
@@ -679,10 +684,10 @@ static void idtentry_exit_cond_resched(struct pt_regs *regs, bool may_sched)
  * This is the last action before returning to the low level ASM code which
  * just needs to return to the appropriate context.
  *
- * Counterpart to idtentry_enter_cond_rcu(). The return value of the entry
- * function must be fed into the @rcu_exit argument.
+ * Counterpart to idtentry_enter(). The return value of the entry
+ * function must be fed into the @state argument.
  */
-void noinstr idtentry_exit_cond_rcu(struct pt_regs *regs, bool rcu_exit)
+noinstr void idtentry_exit(struct pt_regs *regs, idtentry_state_t state)
 {
 	lockdep_assert_irqs_disabled();
 
@@ -695,7 +700,7 @@ void noinstr idtentry_exit_cond_rcu(struct pt_regs *regs, bool rcu_exit)
 		 * carefully and needs the same ordering of lockdep/tracing
 		 * and RCU as the return to user mode path.
 		 */
-		if (rcu_exit) {
+		if (state.exit_rcu) {
 			instrumentation_begin();
 			/* Tell the tracer that IRET will enable interrupts */
 			trace_hardirqs_on_prepare();
@@ -714,7 +719,7 @@ void noinstr idtentry_exit_cond_rcu(struct pt_regs *regs, bool rcu_exit)
 		 * IRQ flags state is correct already. Just tell RCU if it
 		 * was not watching on entry.
 		 */
-		if (rcu_exit)
+		if (state.exit_rcu)
 			rcu_irq_exit();
 	}
 }
@@ -726,7 +731,7 @@ void noinstr idtentry_exit_cond_rcu(struct pt_regs *regs, bool rcu_exit)
  * Invokes enter_from_user_mode() to establish the proper context for
  * NOHZ_FULL. Otherwise scheduling on exit would not be possible.
  */
-void noinstr idtentry_enter_user(struct pt_regs *regs)
+noinstr void idtentry_enter_user(struct pt_regs *regs)
 {
 	check_user_regs(regs);
 	enter_from_user_mode();
@@ -744,13 +749,47 @@ void noinstr idtentry_enter_user(struct pt_regs *regs)
  *
  * Counterpart to idtentry_enter_user().
  */
-void noinstr idtentry_exit_user(struct pt_regs *regs)
+noinstr void idtentry_exit_user(struct pt_regs *regs)
 {
 	lockdep_assert_irqs_disabled();
 
 	prepare_exit_to_usermode(regs);
 }
 
+noinstr bool idtentry_enter_nmi(struct pt_regs *regs)
+{
+	bool irq_state = lockdep_hardirqs_enabled();
+
+	__nmi_enter();
+	lockdep_hardirqs_off(CALLER_ADDR0);
+	lockdep_hardirq_enter();
+	rcu_nmi_enter();
+
+	instrumentation_begin();
+	trace_hardirqs_off_finish();
+	ftrace_nmi_enter();
+	instrumentation_end();
+
+	return irq_state;
+}
+
+noinstr void idtentry_exit_nmi(struct pt_regs *regs, bool restore)
+{
+	instrumentation_begin();
+	ftrace_nmi_exit();
+	if (restore) {
+		trace_hardirqs_on_prepare();
+		lockdep_hardirqs_on_prepare(CALLER_ADDR0);
+	}
+	instrumentation_end();
+
+	rcu_nmi_exit();
+	lockdep_hardirq_exit();
+	if (restore)
+		lockdep_hardirqs_on(CALLER_ADDR0);
+	__nmi_exit();
+}
+
 #ifdef CONFIG_XEN_PV
 #ifndef CONFIG_PREEMPTION
 /*
@@ -800,9 +839,10 @@ static void __xen_pv_evtchn_do_upcall(void)
 __visible noinstr void xen_pv_evtchn_do_upcall(struct pt_regs *regs)
 {
 	struct pt_regs *old_regs;
-	bool inhcall, rcu_exit;
+	bool inhcall;
+	idtentry_state_t state;
 
-	rcu_exit = idtentry_enter_cond_rcu(regs);
+	state = idtentry_enter(regs);
 	old_regs = set_irq_regs(regs);
 
 	instrumentation_begin();
@@ -812,13 +852,13 @@ __visible noinstr void xen_pv_evtchn_do_upcall(struct pt_regs *regs)
 	set_irq_regs(old_regs);
 
 	inhcall = get_and_clear_inhcall();
-	if (inhcall && !WARN_ON_ONCE(rcu_exit)) {
+	if (inhcall && !WARN_ON_ONCE(state.exit_rcu)) {
 		instrumentation_begin();
 		idtentry_exit_cond_resched(regs, true);
 		instrumentation_end();
 		restore_inhcall(inhcall);
 	} else {
-		idtentry_exit_cond_rcu(regs, rcu_exit);
+		idtentry_exit(regs, state);
 	}
 }
 #endif /* CONFIG_XEN_PV */
diff --git a/arch/x86/include/asm/atomic.h b/arch/x86/include/asm/atomic.h
index bf35e476a776..b6cac6e9bb70 100644
--- a/arch/x86/include/asm/atomic.h
+++ b/arch/x86/include/asm/atomic.h
@@ -14,8 +14,6 @@
  * resource counting etc..
  */
 
-#define ATOMIC_INIT(i)	{ (i) }
-
 /**
  * arch_atomic_read - read atomic variable
  * @v: pointer of type atomic_t
diff --git a/arch/x86/include/asm/idtentry.h b/arch/x86/include/asm/idtentry.h
index 80d3b30d3ee3..d74128c964f8 100644
--- a/arch/x86/include/asm/idtentry.h
+++ b/arch/x86/include/asm/idtentry.h
@@ -13,8 +13,15 @@
 void idtentry_enter_user(struct pt_regs *regs);
 void idtentry_exit_user(struct pt_regs *regs);
 
-bool idtentry_enter_cond_rcu(struct pt_regs *regs);
-void idtentry_exit_cond_rcu(struct pt_regs *regs, bool rcu_exit);
+typedef struct idtentry_state {
+	bool exit_rcu;
+} idtentry_state_t;
+
+idtentry_state_t idtentry_enter(struct pt_regs *regs);
+void idtentry_exit(struct pt_regs *regs, idtentry_state_t state);
+
+bool idtentry_enter_nmi(struct pt_regs *regs);
+void idtentry_exit_nmi(struct pt_regs *regs, bool irq_state);
 
 /**
  * DECLARE_IDTENTRY - Declare functions for simple IDT entry points
@@ -54,12 +61,12 @@ static __always_inline void __##func(struct pt_regs *regs);		\
 									\
 __visible noinstr void func(struct pt_regs *regs)			\
 {									\
-	bool rcu_exit = idtentry_enter_cond_rcu(regs);			\
+	idtentry_state_t state = idtentry_enter(regs);			\
 									\
 	instrumentation_begin();					\
 	__##func (regs);						\
 	instrumentation_end();						\
-	idtentry_exit_cond_rcu(regs, rcu_exit);				\
+	idtentry_exit(regs, state);					\
 }									\
 									\
 static __always_inline void __##func(struct pt_regs *regs)
@@ -101,12 +108,12 @@ static __always_inline void __##func(struct pt_regs *regs,		\
 __visible noinstr void func(struct pt_regs *regs,			\
 			    unsigned long error_code)			\
 {									\
-	bool rcu_exit = idtentry_enter_cond_rcu(regs);			\
+	idtentry_state_t state = idtentry_enter(regs);			\
 									\
 	instrumentation_begin();					\
 	__##func (regs, error_code);					\
 	instrumentation_end();						\
-	idtentry_exit_cond_rcu(regs, rcu_exit);				\
+	idtentry_exit(regs, state);					\
 }									\
 									\
 static __always_inline void __##func(struct pt_regs *regs,		\
@@ -199,7 +206,7 @@ static __always_inline void __##func(struct pt_regs *regs, u8 vector);	\
 __visible noinstr void func(struct pt_regs *regs,			\
 			    unsigned long error_code)			\
 {									\
-	bool rcu_exit = idtentry_enter_cond_rcu(regs);			\
+	idtentry_state_t state = idtentry_enter(regs);			\
 									\
 	instrumentation_begin();					\
 	irq_enter_rcu();						\
@@ -207,7 +214,7 @@ __visible noinstr void func(struct pt_regs *regs,			\
 	__##func (regs, (u8)error_code);				\
 	irq_exit_rcu();							\
 	instrumentation_end();						\
-	idtentry_exit_cond_rcu(regs, rcu_exit);				\
+	idtentry_exit(regs, state);					\
 }									\
 									\
 static __always_inline void __##func(struct pt_regs *regs, u8 vector)
@@ -241,7 +248,7 @@ static void __##func(struct pt_regs *regs);				\
 									\
 __visible noinstr void func(struct pt_regs *regs)			\
 {									\
-	bool rcu_exit = idtentry_enter_cond_rcu(regs);			\
+	idtentry_state_t state = idtentry_enter(regs);			\
 									\
 	instrumentation_begin();					\
 	irq_enter_rcu();						\
@@ -249,7 +256,7 @@ __visible noinstr void func(struct pt_regs *regs)			\
 	run_on_irqstack_cond(__##func, regs, regs);			\
 	irq_exit_rcu();							\
 	instrumentation_end();						\
-	idtentry_exit_cond_rcu(regs, rcu_exit);				\
+	idtentry_exit(regs, state);					\
 }									\
 									\
 static noinline void __##func(struct pt_regs *regs)
@@ -270,7 +277,7 @@ static __always_inline void __##func(struct pt_regs *regs);		\
 									\
 __visible noinstr void func(struct pt_regs *regs)			\
 {									\
-	bool rcu_exit = idtentry_enter_cond_rcu(regs);			\
+	idtentry_state_t state = idtentry_enter(regs);			\
 									\
 	instrumentation_begin();					\
 	__irq_enter_raw();						\
@@ -278,7 +285,7 @@ __visible noinstr void func(struct pt_regs *regs)			\
 	__##func (regs);						\
 	__irq_exit_raw();						\
 	instrumentation_end();						\
-	idtentry_exit_cond_rcu(regs, rcu_exit);				\
+	idtentry_exit(regs, state);					\
 }									\
 									\
 static __always_inline void __##func(struct pt_regs *regs)
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index df63786e7bfa..3f78482d9496 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -233,7 +233,7 @@ EXPORT_SYMBOL_GPL(kvm_read_and_reset_apf_flags);
 noinstr bool __kvm_handle_async_pf(struct pt_regs *regs, u32 token)
 {
 	u32 reason = kvm_read_and_reset_apf_flags();
-	bool rcu_exit;
+	idtentry_state_t state;
 
 	switch (reason) {
 	case KVM_PV_REASON_PAGE_NOT_PRESENT:
@@ -243,7 +243,7 @@ noinstr bool __kvm_handle_async_pf(struct pt_regs *regs, u32 token)
 		return false;
 	}
 
-	rcu_exit = idtentry_enter_cond_rcu(regs);
+	state = idtentry_enter(regs);
 	instrumentation_begin();
 
 	/*
@@ -264,7 +264,7 @@ noinstr bool __kvm_handle_async_pf(struct pt_regs *regs, u32 token)
 	}
 
 	instrumentation_end();
-	idtentry_exit_cond_rcu(regs, rcu_exit);
+	idtentry_exit(regs, state);
 	return true;
 }
 
diff --git a/arch/x86/kernel/nmi.c b/arch/x86/kernel/nmi.c
index d7c5e44b26f7..4fc9954a9560 100644
--- a/arch/x86/kernel/nmi.c
+++ b/arch/x86/kernel/nmi.c
@@ -330,7 +330,6 @@ static noinstr void default_do_nmi(struct pt_regs *regs)
 	__this_cpu_write(last_nmi_rip, regs->ip);
 
 	instrumentation_begin();
-	trace_hardirqs_off_finish();
 
 	handled = nmi_handle(NMI_LOCAL, regs);
 	__this_cpu_add(nmi_stats.normal, handled);
@@ -417,8 +416,6 @@ static noinstr void default_do_nmi(struct pt_regs *regs)
 		unknown_nmi_error(reason, regs);
 
 out:
-	if (regs->flags & X86_EFLAGS_IF)
-		trace_hardirqs_on_prepare();
 	instrumentation_end();
 }
 
@@ -478,6 +475,8 @@ static DEFINE_PER_CPU(unsigned long, nmi_dr7);
 
 DEFINE_IDTENTRY_RAW(exc_nmi)
 {
+	bool irq_state;
+
 	if (IS_ENABLED(CONFIG_SMP) && arch_cpu_is_offline(smp_processor_id()))
 		return;
 
@@ -491,14 +490,14 @@ nmi_restart:
 
 	this_cpu_write(nmi_dr7, local_db_save());
 
-	nmi_enter();
+	irq_state = idtentry_enter_nmi(regs);
 
 	inc_irq_stat(__nmi_count);
 
 	if (!ignore_nmis)
 		default_do_nmi(regs);
 
-	nmi_exit();
+	idtentry_exit_nmi(regs, irq_state);
 
 	local_db_restore(this_cpu_read(nmi_dr7));
 
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index b7cb3e0716f7..8493f55e1167 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -245,7 +245,7 @@ static noinstr bool handle_bug(struct pt_regs *regs)
 
 DEFINE_IDTENTRY_RAW(exc_invalid_op)
 {
-	bool rcu_exit;
+	idtentry_state_t state;
 
 	/*
 	 * We use UD2 as a short encoding for 'CALL __WARN', as such
@@ -255,11 +255,11 @@ DEFINE_IDTENTRY_RAW(exc_invalid_op)
 	if (!user_mode(regs) && handle_bug(regs))
 		return;
 
-	rcu_exit = idtentry_enter_cond_rcu(regs);
+	state = idtentry_enter(regs);
 	instrumentation_begin();
 	handle_invalid_op(regs);
 	instrumentation_end();
-	idtentry_exit_cond_rcu(regs, rcu_exit);
+	idtentry_exit(regs, state);
 }
 
 DEFINE_IDTENTRY(exc_coproc_segment_overrun)
@@ -405,7 +405,7 @@ DEFINE_IDTENTRY_DF(exc_double_fault)
 	}
 #endif
 
-	nmi_enter();
+	idtentry_enter_nmi(regs);
 	instrumentation_begin();
 	notify_die(DIE_TRAP, str, regs, error_code, X86_TRAP_DF, SIGSEGV);
 
@@ -651,15 +651,12 @@ DEFINE_IDTENTRY_RAW(exc_int3)
 		instrumentation_end();
 		idtentry_exit_user(regs);
 	} else {
-		nmi_enter();
+		bool irq_state = idtentry_enter_nmi(regs);
 		instrumentation_begin();
-		trace_hardirqs_off_finish();
 		if (!do_int3(regs))
 			die("int3", regs, 0);
-		if (regs->flags & X86_EFLAGS_IF)
-			trace_hardirqs_on_prepare();
 		instrumentation_end();
-		nmi_exit();
+		idtentry_exit_nmi(regs, irq_state);
 	}
 }
 
@@ -867,9 +864,8 @@ out:
 static __always_inline void exc_debug_kernel(struct pt_regs *regs,
 					     unsigned long dr6)
 {
-	nmi_enter();
+	bool irq_state = idtentry_enter_nmi(regs);
 	instrumentation_begin();
-	trace_hardirqs_off_finish();
 
 	/*
 	 * If something gets miswired and we end up here for a user mode
@@ -886,10 +882,8 @@ static __always_inline void exc_debug_kernel(struct pt_regs *regs,
 
 	handle_debug(regs, dr6, false);
 
-	if (regs->flags & X86_EFLAGS_IF)
-		trace_hardirqs_on_prepare();
 	instrumentation_end();
-	nmi_exit();
+	idtentry_exit_nmi(regs, irq_state);
 }
 
 static __always_inline void exc_debug_user(struct pt_regs *regs,
@@ -905,6 +899,7 @@ static __always_inline void exc_debug_user(struct pt_regs *regs,
 	instrumentation_begin();
 
 	handle_debug(regs, dr6, true);
+
 	instrumentation_end();
 	idtentry_exit_user(regs);
 }
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 1ead568c0101..5e41949453cc 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -1377,7 +1377,7 @@ handle_page_fault(struct pt_regs *regs, unsigned long error_code,
 DEFINE_IDTENTRY_RAW_ERRORCODE(exc_page_fault)
 {
 	unsigned long address = read_cr2();
-	bool rcu_exit;
+	idtentry_state_t state;
 
 	prefetchw(&current->mm->mmap_lock);
 
@@ -1412,11 +1412,11 @@ DEFINE_IDTENTRY_RAW_ERRORCODE(exc_page_fault)
 	 * code reenabled RCU to avoid subsequent wreckage which helps
 	 * debugability.
 	 */
-	rcu_exit = idtentry_enter_cond_rcu(regs);
+	state = idtentry_enter(regs);
 
 	instrumentation_begin();
 	handle_page_fault(regs, error_code, address);
 	instrumentation_end();
 
-	idtentry_exit_cond_rcu(regs, rcu_exit);
+	idtentry_exit(regs, state);
 }