x86/entry: Clean up idtentry_enter/exit() leftovers

Now that everything is converted to conditional RCU handling remove
idtentry_enter/exit() and tidy up the conditional functions.

This does not remove rcu_irq_exit_preempt(), to avoid conflicts with the RCU
tree. Will be removed once all of this hits Linus's tree.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Andy Lutomirski <luto@kernel.org>
Link: https://lore.kernel.org/r/20200521202117.473597954@linutronix.de

diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c
index b7fcb13..2a80e4e 100644 (file)
--- a/arch/x86/entry/common.c
+++ b/arch/x86/entry/common.c
@@ -515,7 +515,6 @@ SYSCALL_DEFINE0(ni_syscall)
  * idtentry_enter_cond_rcu - Handle state tracking on idtentry with conditional
  *                          RCU handling
  * @regs:      Pointer to pt_regs of interrupted context
- * @cond_rcu:  Invoke rcu_irq_enter() only if RCU is not watching
  *
  * Invokes:
  *  - lockdep irqflag state tracking as low level ASM entry disabled
@@ -545,14 +544,14 @@ SYSCALL_DEFINE0(ni_syscall)
  * The return value must be fed into the rcu_exit argument of
  * idtentry_exit_cond_rcu().
  */
-bool noinstr idtentry_enter_cond_rcu(struct pt_regs *regs, bool cond_rcu)
+bool noinstr idtentry_enter_cond_rcu(struct pt_regs *regs)
 {
        if (user_mode(regs)) {
                enter_from_user_mode();
                return false;
        }
 
-       if (!cond_rcu || !__rcu_is_watching()) {
+       if (!__rcu_is_watching()) {
                /*
                 * If RCU is not watching then the same careful
                 * sequence vs. lockdep and tracing is required
@@ -608,52 +607,44 @@ void noinstr idtentry_exit_cond_rcu(struct pt_regs *regs, bool rcu_exit)
        if (user_mode(regs)) {
                prepare_exit_to_usermode(regs);
        } else if (regs->flags & X86_EFLAGS_IF) {
+               /*
+                * If RCU was not watching on entry this needs to be done
+                * carefully and needs the same ordering of lockdep/tracing
+                * and RCU as the return to user mode path.
+                */
+               if (rcu_exit) {
+                       instrumentation_begin();
+                       /* Tell the tracer that IRET will enable interrupts */
+                       trace_hardirqs_on_prepare();
+                       lockdep_hardirqs_on_prepare(CALLER_ADDR0);
+                       instrumentation_end();
+                       rcu_irq_exit();
+                       lockdep_hardirqs_on(CALLER_ADDR0);
+                       return;
+               }
+
+               instrumentation_begin();
+
                /* Check kernel preemption, if enabled */
                if (IS_ENABLED(CONFIG_PREEMPTION)) {
-                       /*
-                        * This needs to be done very carefully.
-                        * idtentry_enter() invoked rcu_irq_enter(). This
-                        * needs to be undone before scheduling.
-                        *
-                        * Preemption is disabled inside of RCU idle
-                        * sections. When the task returns from
-                        * preempt_schedule_irq(), RCU is still watching.
-                        *
-                        * rcu_irq_exit_preempt() has additional state
-                        * checking if CONFIG_PROVE_RCU=y
-                        */
                        if (!preempt_count()) {
+                               /* Sanity check RCU and thread stack */
+                               rcu_irq_exit_check_preempt();
                                if (IS_ENABLED(CONFIG_DEBUG_ENTRY))
                                        WARN_ON_ONCE(!on_thread_stack());
-                               instrumentation_begin();
-                               if (rcu_exit)
-                                       rcu_irq_exit_preempt();
                                if (need_resched())
                                        preempt_schedule_irq();
-                               /* Covers both tracing and lockdep */
-                               trace_hardirqs_on();
-                               instrumentation_end();
-                               return;
                        }
                }
-               /*
-                * If preemption is disabled then this needs to be done
-                * carefully with respect to RCU. The exception might come
-                * from a RCU idle section in the idle task due to the fact
-                * that safe_halt() enables interrupts. So this needs the
-                * same ordering of lockdep/tracing and RCU as the return
-                * to user mode path.
-                */
-               instrumentation_begin();
-               /* Tell the tracer that IRET will enable interrupts */
-               trace_hardirqs_on_prepare();
-               lockdep_hardirqs_on_prepare(CALLER_ADDR0);
+               /* Covers both tracing and lockdep */
+               trace_hardirqs_on();
+
                instrumentation_end();
-               if (rcu_exit)
-                       rcu_irq_exit();
-               lockdep_hardirqs_on(CALLER_ADDR0);
        } else {
-               /* IRQ flags state is correct already. Just tell RCU. */
+               /*
+                * IRQ flags state is correct already. Just tell RCU if it
+                * was not watching on entry.
+                */
                if (rcu_exit)
                        rcu_irq_exit();
        }

diff --git a/arch/x86/include/asm/idtentry.h b/arch/x86/include/asm/idtentry.h
index 0f974e5..b056889 100644 (file)
--- a/arch/x86/include/asm/idtentry.h
+++ b/arch/x86/include/asm/idtentry.h
@@ -10,19 +10,9 @@
 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, bool cond_rcu);
+bool idtentry_enter_cond_rcu(struct pt_regs *regs);
 void idtentry_exit_cond_rcu(struct pt_regs *regs, bool rcu_exit);
 
-static __always_inline void idtentry_enter(struct pt_regs *regs)
-{
-       idtentry_enter_cond_rcu(regs, false);
-}
-
-static __always_inline void idtentry_exit(struct pt_regs *regs)
-{
-       idtentry_exit_cond_rcu(regs, true);
-}
-
 /**
  * DECLARE_IDTENTRY - Declare functions for simple IDT entry points
  *                   No error code pushed by hardware