From: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>,
Peter Zijlstra <peterz@infradead.org>,
Ananth N Mavinakayanahalli <ananth@in.ibm.com>,
Anton Arapov <anton@redhat.com>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 4/5] uprobes: Kill UTASK_BP_HIT state
Date: Thu, 20 Sep 2012 19:36:09 +0530 [thread overview]
Message-ID: <20120920140609.GD27880@linux.vnet.ibm.com> (raw)
In-Reply-To: <20120914171600.GA29649@redhat.com>
* 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, ¤t->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
>
next prev parent reply other threads:[~2012-09-20 14:16 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-14 17:15 [PATCH 0/5] uprobes: handle_swbp() fixes Oleg Nesterov
2012-09-14 17:15 ` [PATCH 1/5] uprobes: Do not leak UTASK_BP_HIT if find_active_uprobe() fails Oleg Nesterov
2012-09-14 17:35 ` Oleg Nesterov
2012-09-20 13:53 ` Srikar Dronamraju
2012-09-14 17:15 ` [PATCH 2/5] uprobes: Do not setup ->active_uprobe/state prematurely Oleg Nesterov
2012-09-20 13:55 ` Srikar Dronamraju
2012-09-14 17:15 ` [PATCH 3/5] uprobes: Fix UPROBE_SKIP_SSTEP checks in handle_swbp() Oleg Nesterov
2012-09-15 7:39 ` Ananth N Mavinakayanahalli
2012-09-15 15:01 ` Oleg Nesterov
2012-09-17 17:20 ` Srikar Dronamraju
2012-09-18 16:07 ` Oleg Nesterov
2012-09-20 14:43 ` Srikar Dronamraju
2012-09-24 20:08 ` Oleg Nesterov
2012-09-29 17:42 ` Oleg Nesterov
2012-09-20 14:05 ` Srikar Dronamraju
2012-09-14 17:16 ` [PATCH 4/5] uprobes: Kill UTASK_BP_HIT state Oleg Nesterov
2012-09-16 14:38 ` Oleg Nesterov
2012-09-20 14:06 ` Srikar Dronamraju [this message]
2012-09-14 17:16 ` [PATCH 5/5] uprobes: Move clear_thread_flag(TIF_UPROBE) to uprobe_notify_resume() Oleg Nesterov
2012-09-20 14:06 ` Srikar Dronamraju
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