uprobes: Remove now-redundant smp_read_barrier_depends() (5c6338b4) · Commits · 戴 / test

Now that READ_ONCE() implies smp_read_barrier_depends(), the get_xol_area() and get_trampoline_vaddr() no longer need their smp_read_barrier_depends() calls, which this commit removes. While we are here, convert the corresponding smp_wmb() to an smp_store_release(). Signed-off-by:

Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Arnaldo Carvalho de Melo <acme@kernel.org> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>

kernel/events/uprobes.c

+6 −6

Original line number	Diff line number	Diff line
		@@ -1167,8 +1167,8 @@ static int xol_add_vma(struct mm_struct mm, struct xol_area area)
		}

		ret = 0;
		smp_wmb(); /* pairs with get_xol_area() */
		mm->uprobes_state.xol_area = area;
		/* pairs with get_xol_area() */
		smp_store_release(&mm->uprobes_state.xol_area, area); /* ^^^ */
		fail:
		up_write(&mm->mmap_sem);

		@@ -1230,8 +1230,8 @@ static struct xol_area *get_xol_area(void)
		if (!mm->uprobes_state.xol_area)
		__create_xol_area(0);

		area = mm->uprobes_state.xol_area;
		smp_read_barrier_depends(); /* pairs with wmb in xol_add_vma() */
		/* Pairs with xol_add_vma() smp_store_release() */
		area = READ_ONCE(mm->uprobes_state.xol_area); /* ^^^ */
		return area;
		}

		@@ -1528,8 +1528,8 @@ static unsigned long get_trampoline_vaddr(void)
		struct xol_area *area;
		unsigned long trampoline_vaddr = -1;

		area = current->mm->uprobes_state.xol_area;
		smp_read_barrier_depends();
		/* Pairs with xol_add_vma() smp_store_release() */
		area = READ_ONCE(current->mm->uprobes_state.xol_area); /* ^^^ */
		if (area)
		trampoline_vaddr = area->vaddr;

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