* Oleg Nesterov <o...@redhat.com> [2012-12-31 18:52:29]:
> handle_swbp() does get_utask() before can_skip_sstep() for no reason,
> we do not need ->utask if can_skip_sstep() succeeds.
>
> Move get_utask() to pre_ssout() who actually starts to use it. Move
> the initialization of utask->active_uprobe/state as well. This way
> the whole initialization is consolidated in pre_ssout().
>
> Signed-off-by: Oleg Nesterov <o...@redhat.com>
> ---
> kernel/events/uprobes.c | 16 ++++++----------
> 1 files changed, 6 insertions(+), 10 deletions(-)
>
> diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
> index bd94d2c..ad1245d 100644
> --- a/kernel/events/uprobes.c
> +++ b/kernel/events/uprobes.c
> @@ -1308,7 +1308,9 @@ pre_ssout(struct uprobe *uprobe, struct pt_regs *regs,
> unsigned long bp_vaddr)
> unsigned long xol_vaddr;
> int err;
>
> - utask = current->utask;
> + utask = get_utask();
> + if (!utask)
> + return -ENOMEM;
>
> xol_vaddr = xol_get_insn_slot(uprobe);
> if (!xol_vaddr)
> @@ -1323,6 +1325,8 @@ pre_ssout(struct uprobe *uprobe, struct pt_regs *regs,
> unsigned long bp_vaddr)
> return err;
> }
>
> + utask->active_uprobe = uprobe;
> + utask->state = UTASK_SSTEP;
> return 0;
> }
>
> @@ -1474,7 +1478,6 @@ static void handler_chain(struct uprobe *uprobe, struct
> pt_regs *regs)
> */
> static void handle_swbp(struct pt_regs *regs)
> {
> - struct uprobe_task *utask;
> struct uprobe *uprobe;
> unsigned long bp_vaddr;
> int uninitialized_var(is_swbp);
> @@ -1512,19 +1515,12 @@ static void handle_swbp(struct pt_regs *regs)
> if (unlikely(!test_bit(UPROBE_COPY_INSN, &uprobe->flags)))
> goto out;
>
> - utask = get_utask();
> - if (!utask)
> - goto out; /* re-execute the instruction. */
> -
If get_utask fails with the above change, Dont we end up calling
handler_chain twice(or more)?. I think this is probably true with
previous patch too.
> handler_chain(uprobe, regs);
> if (can_skip_sstep(uprobe, regs))
> goto out;
>
> - if (!pre_ssout(uprobe, regs, bp_vaddr)) {
> - utask->active_uprobe = uprobe;
> - utask->state = UTASK_SSTEP;
> + if (!pre_ssout(uprobe, regs, bp_vaddr))
> return;
> - }
>
> /* can_skip_sstep() succeeded, or restart if can't singlestep */
> out:
> --
> 1.5.5.1
>
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