uprobes: Do not allocate current->utask unnecessary
Oleg Nesterov [Mon, 31 Dec 2012 17:20:42 +0000 (18:20 +0100)]
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 <oleg@redhat.com>
Acked-by: Anton Arapov <anton@redhat.com>

kernel/events/uprobes.c

index 0527379..071edcb 100644 (file)
@@ -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. */
-
        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: