This is a note to let you know that I've just added the patch titled
kernel/fork.c: virtually mapped stacks: do not disable interrupts
to the 4.12-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
kernel-fork.c-virtually-mapped-stacks-do-not-disable-interrupts.patch
and it can be found in the queue-4.12 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 112166f88cf83dd11486cf1818672d42b540865b Mon Sep 17 00:00:00 2001
From: Christoph Lameter <cl@xxxxxxxxx>
Date: Wed, 12 Jul 2017 14:33:11 -0700
Subject: kernel/fork.c: virtually mapped stacks: do not disable interrupts
From: Christoph Lameter <cl@xxxxxxxxx>
commit 112166f88cf83dd11486cf1818672d42b540865b upstream.
The reason to disable interrupts seems to be to avoid switching to a
different processor while handling per cpu data using individual loads and
stores. If we use per cpu RMV primitives we will not have to disable
interrupts.
Link: http://lkml.kernel.org/r/alpine.DEB.2.20.1705171055130.5898@xxxxxxxxxxxxxxx
Signed-off-by: Christoph Lameter <cl@xxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/fork.c | 16 +++++-----------
1 file changed, 5 insertions(+), 11 deletions(-)
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -205,19 +205,17 @@ static unsigned long *alloc_thread_stack
void *stack;
int i;
- local_irq_disable();
for (i = 0; i < NR_CACHED_STACKS; i++) {
- struct vm_struct *s = this_cpu_read(cached_stacks[i]);
+ struct vm_struct *s;
+
+ s = this_cpu_xchg(cached_stacks[i], NULL);
if (!s)
continue;
- this_cpu_write(cached_stacks[i], NULL);
tsk->stack_vm_area = s;
- local_irq_enable();
return s->addr;
}
- local_irq_enable();
stack = __vmalloc_node_range(THREAD_SIZE, THREAD_SIZE,
VMALLOC_START, VMALLOC_END,
@@ -245,19 +243,15 @@ static inline void free_thread_stack(str
{
#ifdef CONFIG_VMAP_STACK
if (task_stack_vm_area(tsk)) {
- unsigned long flags;
int i;
- local_irq_save(flags);
for (i = 0; i < NR_CACHED_STACKS; i++) {
- if (this_cpu_read(cached_stacks[i]))
+ if (this_cpu_cmpxchg(cached_stacks[i],
+ NULL, tsk->stack_vm_area) != NULL)
continue;
- this_cpu_write(cached_stacks[i], tsk->stack_vm_area);
- local_irq_restore(flags);
return;
}
- local_irq_restore(flags);
vfree_atomic(tsk->stack);
return;
Patches currently in stable-queue which might be from cl@xxxxxxxxx are
queue-4.12/kernel-fork.c-virtually-mapped-stacks-do-not-disable-interrupts.patch