+ kcov-avoid-enabledisable-interrupts-if-in_task.patch added to -mm tree

[akpm@linux-foundation.org]

The patch titled
     Subject: kcov: avoid enable+disable interrupts if !in_task()
has been added to the -mm tree.  Its filename is
     kcov-avoid-enabledisable-interrupts-if-in_task.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/kcov-avoid-enabledisable-interrupts-if-in_task.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/kcov-avoid-enabledisable-interrupts-if-in_task.patch

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------------------------------------------------------
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Subject: 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.

Link: https://lkml.kernel.org/r/20210923164741.1859522-5-bigeasy@linutronix.de
Link: https://lore.kernel.org/r/20210830172627.267989-5-bigeasy@linutronix.de
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Acked-by: Dmitry Vyukov <dvyukov@google.com>
Acked-by: Marco Elver <elver@google.com>
Tested-by: Marco Elver <elver@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Clark Williams <williams@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 kernel/kcov.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/kernel/kcov.c~kcov-avoid-enabledisable-interrupts-if-in_task
+++ a/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;
 
_

Patches currently in -mm which might be from bigeasy@linutronix.de are

mm-disable-zsmalloc-on-preempt_rt.patch
documentation-kcov-include-typesh-in-the-example.patch
documentation-kcov-define-ip-in-the-example.patch
kcov-allocate-per-cpu-memory-on-the-relevant-node.patch
kcov-avoid-enabledisable-interrupts-if-in_task.patch
kcov-replace-local_irq_save-with-a-local_lock_t.patch