linux-kernel - [PATCH v2 4/5] kcov: Avoid enable+disable interrupts if !in

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Message-Id: <20210923164741.1859522-5-bigeasy@linutronix.de>
Date:   Thu, 23 Sep 2021 18:47:40 +0200
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     kasan-dev@...glegroups.com, linux-kernel@...r.kernel.org
Cc:     Dmitry Vyukov <dvyukov@...gle.com>,
        Andrey Konovalov <andreyknvl@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Steven Rostedt <rostedt@...dmis.org>,
        Marco Elver <elver@...gle.com>,
        Clark Williams <williams@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Subject: [PATCH v2 4/5] kcov: Avoid enable+disable interrupts if !in_task().

kcov_remote_start() may need to allocate memory in the in_task() case
(otherwise per-CPU memory has been pre-allocated) and therefore requires
enabled interrupts.
The interrupts are enabled before checking if the allocation is required
so if no allocation is required then the interrupts are needlessly
enabled and disabled again.

Enable interrupts only if memory allocation is performed.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Acked-by: Dmitry Vyukov <dvyukov@...gle.com>
Acked-by: Marco Elver <elver@...gle.com>
Tested-by: Marco Elver <elver@...gle.com>
Link: https://lore.kernel.org/r/20210830172627.267989-5-bigeasy@linutronix.de
---
 kernel/kcov.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/kernel/kcov.c b/kernel/kcov.c
index 4f910231d99a2..620dc4ffeb685 100644
--- a/kernel/kcov.c
+++ b/kernel/kcov.c
@@ -869,19 +869,19 @@ void kcov_remote_start(u64 handle)
 		size = CONFIG_KCOV_IRQ_AREA_SIZE;
 		area = this_cpu_ptr(&kcov_percpu_data)->irq_area;
 	}
-	spin_unlock_irqrestore(&kcov_remote_lock, flags);
+	spin_unlock(&kcov_remote_lock);
 
 	/* Can only happen when in_task(). */
 	if (!area) {
+		local_irqrestore(flags);
 		area = vmalloc(size * sizeof(unsigned long));
 		if (!area) {
 			kcov_put(kcov);
 			return;
 		}
+		local_irq_save(flags);
 	}
 
-	local_irq_save(flags);
-
 	/* Reset coverage size. */
 	*(u64 *)area = 0;
 
-- 
2.33.0