linux-kernel - [tip: irq/core] irq: Call tick_irq_enter() inside HARDIRQ

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Message-ID: <160693699084.3364.1887616358916715412.tip-bot2@tip-bot2>
Date:   Wed, 02 Dec 2020 19:23:10 -0000
From:   "tip-bot2 for Frederic Weisbecker" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Frederic Weisbecker <frederic@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>, x86@...nel.org,
        linux-kernel@...r.kernel.org, maz@...nel.org
Subject: [tip: irq/core] irq: Call tick_irq_enter() inside HARDIRQ_OFFSET

The following commit has been merged into the irq/core branch of tip:

Commit-ID:     d14ce74f1fb376ccbbc0b05ded477ada51253729
Gitweb:        https://git.kernel.org/tip/d14ce74f1fb376ccbbc0b05ded477ada51253729
Author:        Frederic Weisbecker <frederic@...nel.org>
AuthorDate:    Wed, 02 Dec 2020 12:57:32 +01:00
Committer:     Thomas Gleixner <tglx@...utronix.de>
CommitterDate: Wed, 02 Dec 2020 20:20:05 +01:00

irq: Call tick_irq_enter() inside HARDIRQ_OFFSET

Now that account_hardirq_enter() is called after HARDIRQ_OFFSET has
been incremented, there is nothing left that prevents us from also
moving tick_irq_enter() after HARDIRQ_OFFSET is incremented.

The desired outcome is to remove the nasty hack that prevents softirqs
from being raised through ksoftirqd instead of the hardirq bottom half.
Also tick_irq_enter() then becomes appropriately covered by lockdep.

Signed-off-by: Frederic Weisbecker <frederic@...nel.org>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Link: https://lore.kernel.org/r/20201202115732.27827-6-frederic@kernel.org

---
 kernel/softirq.c | 14 +++++---------
 1 file changed, 5 insertions(+), 9 deletions(-)

diff --git a/kernel/softirq.c b/kernel/softirq.c
index b8f42b3..d5bfd5e 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -377,16 +377,12 @@ restart:
  */
 void irq_enter_rcu(void)
 {
-	if (is_idle_task(current) && !in_interrupt()) {
-		/*
-		 * Prevent raise_softirq from needlessly waking up ksoftirqd
-		 * here, as softirq will be serviced on return from interrupt.
-		 */
-		local_bh_disable();
+	__irq_enter_raw();
+
+	if (is_idle_task(current) && (irq_count() == HARDIRQ_OFFSET))
 		tick_irq_enter();
-		_local_bh_enable();
-	}
-	__irq_enter();
+
+	account_hardirq_enter(current);
 }
 
 /**