lkml.org 
[lkml]   [2012]   [Sep]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 4/5] uprobes: Kill UTASK_BP_HIT state
* Oleg Nesterov <oleg@redhat.com> [2012-09-14 19:16:00]:

> Kill UTASK_BP_HIT state, it buys nothing but complicates the code.
> It is only used in uprobe_notify_resume() to decide who should be
> called, we can check utask->active_uprobe != NULL instead. And this
> allows us to simplify handle_swbp(), no need to clear utask->state.
>
> Likewise we could kill UTASK_SSTEP, but UTASK_BP_HIT is worse and
> imho should die. The problem is, it creates the special case when
> task->utask is NULL, we can't distinguish RUNNING and BP_HIT. With
> his patch utask == NULL always means RUNNING.
>
> Signed-off-by: Oleg Nesterov <oleg@redhat.com>


Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>

> ---
> include/linux/uprobes.h | 1 -
> kernel/events/uprobes.c | 29 +++++++++--------------------
> 2 files changed, 9 insertions(+), 21 deletions(-)
>
> diff --git a/include/linux/uprobes.h b/include/linux/uprobes.h
> index e6f0331..18d839d 100644
> --- a/include/linux/uprobes.h
> +++ b/include/linux/uprobes.h
> @@ -59,7 +59,6 @@ struct uprobe_consumer {
> #ifdef CONFIG_UPROBES
> enum uprobe_task_state {
> UTASK_RUNNING,
> - UTASK_BP_HIT,
> UTASK_SSTEP,
> UTASK_SSTEP_ACK,
> UTASK_SSTEP_TRAPPED,
> diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
> index 403d2e0..4ea0f0b 100644
> --- a/kernel/events/uprobes.c
> +++ b/kernel/events/uprobes.c
> @@ -1469,10 +1469,6 @@ static void handle_swbp(struct pt_regs *regs)
> bp_vaddr = uprobe_get_swbp_addr(regs);
> uprobe = find_active_uprobe(bp_vaddr, &is_swbp);
>
> - utask = current->utask;
> - if (utask)
> - utask->state = UTASK_RUNNING;
> -
> if (!uprobe) {
> if (is_swbp > 0) {
> /* No matching uprobe; signal SIGTRAP. */
> @@ -1491,6 +1487,7 @@ static void handle_swbp(struct pt_regs *regs)
> return;
> }
>
> + utask = current->utask;
> if (!utask) {
> utask = add_utask();
> /* Cannot allocate; re-execute the instruction. */
> @@ -1547,13 +1544,12 @@ static void handle_singlestep(struct uprobe_task *utask, struct pt_regs *regs)
> }
>
> /*
> - * On breakpoint hit, breakpoint notifier sets the TIF_UPROBE flag. (and on
> - * subsequent probe hits on the thread sets the state to UTASK_BP_HIT) and
> - * allows the thread to return from interrupt.
> + * On breakpoint hit, breakpoint notifier sets the TIF_UPROBE flag and
> + * allows the thread to return from interrupt. After that handle_swbp()
> + * sets utask->active_uprobe.
> *
> - * On singlestep exception, singlestep notifier sets the TIF_UPROBE flag and
> - * also sets the state to UTASK_SSTEP_ACK and allows the thread to return from
> - * interrupt.
> + * On singlestep exception, singlestep notifier sets the TIF_UPROBE flag
> + * and allows the thread to return from interrupt.
> *
> * While returning to userspace, thread notices the TIF_UPROBE flag and calls
> * uprobe_notify_resume().
> @@ -1563,10 +1559,10 @@ void uprobe_notify_resume(struct pt_regs *regs)
> struct uprobe_task *utask;
>
> utask = current->utask;
> - if (!utask || utask->state == UTASK_BP_HIT)
> - handle_swbp(regs);
> - else
> + if (utask && utask->active_uprobe)
> handle_singlestep(utask, regs);
> + else
> + handle_swbp(regs);
> }
>
> /*
> @@ -1575,17 +1571,10 @@ void uprobe_notify_resume(struct pt_regs *regs)
> */
> int uprobe_pre_sstep_notifier(struct pt_regs *regs)
> {
> - struct uprobe_task *utask;
> -
> if (!current->mm || !test_bit(MMF_HAS_UPROBES, &current->mm->flags))
> return 0;
>
> - utask = current->utask;
> - if (utask)
> - utask->state = UTASK_BP_HIT;
> -
> set_thread_flag(TIF_UPROBE);
> -
> return 1;
> }
>
> --
> 1.5.5.1
>



\
 
 \ /
  Last update: 2012-09-20 16:41    [W:0.131 / U:0.240 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site