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Message-Id: <20200521202117.473597954@linutronix.de>
Date: Thu, 21 May 2020 22:05:20 +0200
From: Thomas Gleixner <tglx@...utronix.de>
To: LKML <linux-kernel@...r.kernel.org>
Cc: Andy Lutomirski <luto@...nel.org>,
Andrew Cooper <andrew.cooper3@...rix.com>,
X86 ML <x86@...nel.org>,
"Paul E. McKenney" <paulmck@...nel.org>,
Alexandre Chartre <alexandre.chartre@...cle.com>,
Frederic Weisbecker <frederic@...nel.org>,
Paolo Bonzini <pbonzini@...hat.com>,
Sean Christopherson <sean.j.christopherson@...el.com>,
Masami Hiramatsu <mhiramat@...nel.org>,
Petr Mladek <pmladek@...e.com>,
Steven Rostedt <rostedt@...dmis.org>,
Joel Fernandes <joel@...lfernandes.org>,
Boris Ostrovsky <boris.ostrovsky@...cle.com>,
Juergen Gross <jgross@...e.com>,
Brian Gerst <brgerst@...il.com>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
Josh Poimboeuf <jpoimboe@...hat.com>,
Will Deacon <will@...nel.org>,
Tom Lendacky <thomas.lendacky@....com>,
Wei Liu <wei.liu@...nel.org>,
Michael Kelley <mikelley@...rosoft.com>,
Jason Chen CJ <jason.cj.chen@...el.com>,
Zhao Yakui <yakui.zhao@...el.com>,
"Peter Zijlstra (Intel)" <peterz@...radead.org>
Subject: [patch V9 07/39] x86/entry: Cleanup 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 hit Linus tree.
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
V9: New patch
---
arch/x86/entry/common.c | 67 +++++++++++++++++-----------------------
arch/x86/include/asm/idtentry.h | 12 -------
2 files changed, 30 insertions(+), 49 deletions(-)
--- 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
@@ -545,12 +544,12 @@ 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();
} else {
- 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
@@ -605,52 +604,44 @@ void noinstr idtentry_exit_cond_rcu(stru
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();
}
--- 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
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