Commit-ID: 499a4f3ec057a0f79636cc3c1e581bb6e977a30f
Gitweb: http://git.kernel.org/tip/499a4f3ec057a0f79636cc3c1e581bb6e977a30f
Author: Oleg Nesterov <oleg@xxxxxxxxxx>
AuthorDate: Sun, 19 Aug 2012 17:41:34 +0200
Committer: Oleg Nesterov <oleg@xxxxxxxxxx>
CommitDate: Sat, 15 Sep 2012 17:37:27 +0200
uprobes: Teach find_active_uprobe() to clear MMF_HAS_UPROBES
The wrong MMF_HAS_UPROBES doesn't really hurt, just it triggers
the "slow" and unnecessary handle_swbp() path if the task hits
the non-uprobe breakpoint.
So this patch changes find_active_uprobe() to check every valid
vma and clear MMF_HAS_UPROBES if no uprobes were found. This is
adds the slow O(n) path, but it is only called in unlikely case
when the task hits the normal breakpoint first time after
uprobe_unregister().
Note the "not strictly accurate" comment in mmf_recalc_uprobes().
We can fix this, we only need to teach vma_has_uprobes() to return
a bit more more info, but I am not sure this worth the trouble.
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Acked-by: Srikar Dronamraju <srikar@xxxxxxxxxxxxxxxxxx>
---
kernel/events/uprobes.c | 22 ++++++++++++++++++++++
1 files changed, 22 insertions(+), 0 deletions(-)
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 9a7f08b..e4a906c 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -1396,6 +1396,25 @@ static bool can_skip_sstep(struct uprobe *uprobe, struct pt_regs *regs)
return false;
}
+static void mmf_recalc_uprobes(struct mm_struct *mm)
+{
+ struct vm_area_struct *vma;
+
+ for (vma = mm->mmap; vma; vma = vma->vm_next) {
+ if (!valid_vma(vma, false))
+ continue;
+ /*
+ * This is not strictly accurate, we can race with
+ * uprobe_unregister() and see the already removed
+ * uprobe if delete_uprobe() was not yet called.
+ */
+ if (vma_has_uprobes(vma, vma->vm_start, vma->vm_end))
+ return;
+ }
+
+ clear_bit(MMF_HAS_UPROBES, &mm->flags);
+}
+
static struct uprobe *find_active_uprobe(unsigned long bp_vaddr, int *is_swbp)
{
struct mm_struct *mm = current->mm;
@@ -1417,6 +1436,9 @@ static struct uprobe *find_active_uprobe(unsigned long bp_vaddr, int *is_swbp)
} else {
*is_swbp = -EFAULT;
}
+
+ if (!uprobe && test_and_clear_bit(MMF_RECALC_UPROBES, &mm->flags))
+ mmf_recalc_uprobes(mm);
up_read(&mm->mmap_sem);
return uprobe;
--
To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
|