linux-kernel - [patch V9 12/39] x86/entry: Split out idtentry_exit_cond

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Date:   Thu, 21 May 2020 22:05:25 +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 12/39] x86/entry: Split out idtentry_exit_cond_resched()

The XEN PV hypercall requires the ability of conditional rescheduling when
preemption is disabled because some hypercalls take ages.

Split out the rescheduling code from idtentry_exit_cond_rcu() so it can
be reused for that.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
V9: New patch
---
 arch/x86/entry/common.c |   30 +++++++++++++++---------------
 1 file changed, 15 insertions(+), 15 deletions(-)

--- a/arch/x86/entry/common.c
+++ b/arch/x86/entry/common.c
@@ -580,6 +580,20 @@ bool noinstr idtentry_enter_cond_rcu(str
 	return false;
 }
 
+static void idtentry_exit_cond_resched(struct pt_regs *regs, bool may_sched)
+{
+	if (may_sched && !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());
+		if (need_resched())
+			preempt_schedule_irq();
+	}
+	/* Covers both tracing and lockdep */
+	trace_hardirqs_on();
+}
+
 /**
  * idtentry_exit_cond_rcu - Handle return from exception with conditional RCU
  *			    handling
@@ -621,21 +635,7 @@ void noinstr idtentry_exit_cond_rcu(stru
 		}
 
 		instrumentation_begin();
-
-		/* Check kernel preemption, if enabled */
-		if (IS_ENABLED(CONFIG_PREEMPTION)) {
-			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());
-				if (need_resched())
-					preempt_schedule_irq();
-			}
-		}
-		/* Covers both tracing and lockdep */
-		trace_hardirqs_on();
-
+		idtentry_exit_cond_resched(regs, IS_ENABLED(CONFIG_PREEMPTION));
 		instrumentation_end();
 	} else {
 		/*