On Sun, Nov 25, 2012 at 11:33:44PM +0100, Oleg Nesterov wrote:
> uprobe_events counts the number of uprobes in uprobes_tree but
> it is used as a boolean. We can use RB_EMPTY_ROOT() instead.
>
> Probably no_uprobe_events() added by this patch can have more
> callers, say, mmf_recalc_uprobes().
>
> Signed-off-by: Oleg Nesterov <o...@redhat.com>
> ---
> kernel/events/uprobes.c | 19 +++++++------------
> 1 files changed, 7 insertions(+), 12 deletions(-)
Acked-by: Anton Arapov <an...@redhat.com>
> diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
> index 1e047f8..53dc2eb 100644
> --- a/kernel/events/uprobes.c
> +++ b/kernel/events/uprobes.c
> @@ -41,6 +41,11 @@
> #define MAX_UPROBE_XOL_SLOTS UINSNS_PER_PAGE
>
> static struct rb_root uprobes_tree = RB_ROOT;
> +/*
> + * allows us to skip the uprobe_mmap if there are no uprobe events active
> + * at this time. Probably a fine grained per inode count is better?
> + */
> +#define no_uprobe_events() RB_EMPTY_ROOT(&uprobes_tree)
>
> static DEFINE_SPINLOCK(uprobes_treelock); /* serialize rbtree access */
>
> @@ -74,13 +79,6 @@ static struct mutex uprobes_mmap_mutex[UPROBES_HASH_SZ];
>
> static struct percpu_rw_semaphore dup_mmap_sem;
>
> -/*
> - * uprobe_events allows us to skip the uprobe_mmap if there are no uprobe
> - * events active at this time. Probably a fine grained per inode count is
> - * better?
> - */
> -static atomic_t uprobe_events = ATOMIC_INIT(0);
> -
> /* Have a copy of original instruction */
> #define UPROBE_COPY_INSN 0
> /* Can skip singlestep */
> @@ -460,8 +458,6 @@ static struct uprobe *alloc_uprobe(struct inode *inode,
> loff_t offset)
> kfree(uprobe);
> uprobe = cur_uprobe;
> iput(inode);
> - } else {
> - atomic_inc(&uprobe_events);
> }
>
> return uprobe;
> @@ -685,7 +681,6 @@ static void delete_uprobe(struct uprobe *uprobe)
> spin_unlock(&uprobes_treelock);
> iput(uprobe->inode);
> put_uprobe(uprobe);
> - atomic_dec(&uprobe_events);
> }
>
> struct map_info {
> @@ -975,7 +970,7 @@ int uprobe_mmap(struct vm_area_struct *vma)
> struct uprobe *uprobe, *u;
> struct inode *inode;
>
> - if (!atomic_read(&uprobe_events) || !valid_vma(vma, true))
> + if (no_uprobe_events() || !valid_vma(vma, true))
> return 0;
>
> inode = vma->vm_file->f_mapping->host;
> @@ -1021,7 +1016,7 @@ vma_has_uprobes(struct vm_area_struct *vma, unsigned
> long start, unsigned long e
> */
> void uprobe_munmap(struct vm_area_struct *vma, unsigned long start, unsigned
> long end)
> {
> - if (!atomic_read(&uprobe_events) || !valid_vma(vma, false))
> + if (no_uprobe_events() || !valid_vma(vma, false))
> return;
>
> if (!atomic_read(&vma->vm_mm->mm_users)) /* called by mmput() ? */
> --
> 1.5.5.1
>
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