kernel/fork.c: virtually mapped stacks: do not disable interrupts (112166f8) · Commits · 戴 / test

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@east.gentwo.org Signed-off-by:

Christoph Lameter <cl@linux.com> Cc: Andy Lutomirski <luto@amacapital.net> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

kernel/fork.c

+5 −11

Original line number	Diff line number	Diff line
		@@ -205,19 +205,17 @@ static unsigned long alloc_thread_stack_node(struct task_struct tsk, int node)
		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(struct task_struct *tsk)
		{
		#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;

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