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>
Reviewed-by: 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>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/kernel/kcov.c b/kernel/kcov.c
index 4f910231d99a20e6fb4c37fe38197bcc66b6261e..620dc4ffeb685a2ff9ea0d272fdf3e79843f2871 100644 (file)
--- 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;