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Date: Thu, 3 Jan 2013 14:34:39 +0530 From: Srikar Dronamraju <srikar@...ux.vnet.ibm.com> To: Oleg Nesterov <oleg@...hat.com> Cc: Ingo Molnar <mingo@...e.hu>, Peter Zijlstra <peterz@...radead.org>, Ananth N Mavinakayanahalli <ananth@...ibm.com>, Anton Arapov <anton@...hat.com>, linux-kernel@...r.kernel.org Subject: Re: [PATCH 2/3] uprobes: Introduce uprobe_is_active() * Oleg Nesterov <oleg@...hat.com> [2012-11-25 23:33:47]: > The lifetime of uprobe->rb_node and uprobe->inode is not refcounted, > delete_uprobe() is called when we detect that uprobe has no consumers, > and it would be deadly wrong to do this twice. > > Change delete_uprobe() to WARN() if it was already called. We use > RB_CLEAR_NODE() to mark uprobe "inactive", then RB_EMPTY_NODE() can > be used to detect this case. > > RB_EMPTY_NODE() is not used directly, we add the trivial helper for > the next change. > > Signed-off-by: Oleg Nesterov <oleg@...hat.com> Acked-by: Srikar Dronamraju <srikar@...ux.vnet.ibm.com> > --- > kernel/events/uprobes.c | 8 ++++++++ > 1 files changed, 8 insertions(+), 0 deletions(-) > > diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c > index 53dc2eb..2886c82 100644 > --- a/kernel/events/uprobes.c > +++ b/kernel/events/uprobes.c > @@ -669,6 +669,10 @@ remove_breakpoint(struct uprobe *uprobe, struct mm_struct *mm, unsigned long vad > return set_orig_insn(&uprobe->arch, mm, vaddr); > } > > +static inline bool uprobe_is_active(struct uprobe *uprobe) > +{ > + return !RB_EMPTY_NODE(&uprobe->rb_node); > +} > /* > * There could be threads that have already hit the breakpoint. They > * will recheck the current insn and restart if find_uprobe() fails. > @@ -676,9 +680,13 @@ remove_breakpoint(struct uprobe *uprobe, struct mm_struct *mm, unsigned long vad > */ > static void delete_uprobe(struct uprobe *uprobe) > { > + if (WARN_ON(!uprobe_is_active(uprobe))) > + return; > + > spin_lock(&uprobes_treelock); > rb_erase(&uprobe->rb_node, &uprobes_tree); > spin_unlock(&uprobes_treelock); > + RB_CLEAR_NODE(&uprobe->rb_node); /* for uprobe_is_active() */ > iput(uprobe->inode); > put_uprobe(uprobe); > } > -- > 1.5.5.1 > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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