Re: [PATCH v5 3.1.0-rc4-tip 12/26] Uprobes: Handle breakpointand Singlestep
From: Oleg Nesterov
Date: Wed Oct 05 2011 - 13:53:06 EST
On 09/26, Peter Zijlstra wrote:
> On Mon, 2011-09-26 at 21:31 +0530, Srikar Dronamraju wrote:
> > * Peter Zijlstra <peterz@xxxxxxxxxxxxx> [2011-09-26 15:59:13]:
> > > On Tue, 2011-09-20 at 17:32 +0530, Srikar Dronamraju wrote:
> > > > Hence provide some extra
> > > > + * time (by way of synchronize_sched() for breakpoint hit threads to acquire
> > > > + * the uprobes_treelock before the uprobe is removed from the rbtree.
> > >
> > > 'Some extra time' doesn't make me all warm an fuzzy inside, but instead
> > > screams we fudge around a race condition.
> > The extra time provided is sufficient to avoid the race. So will modify
> > it to mean "sufficient" instead of "some".
> > Would that suffice?
> Much better, for extra point, explain why its sufficient as well ;-)
I can't understand why synchronize_sched helps. In fact it is very
possible I simply misunderstood the problem, I'll appreciate if you
Just for example. Suppose that uprobe_notify_resume() sleeps in
down_read(mmap_sem). In this case synchronize_sched() can return
even before it takes this sem, how this can help the subsequent
find_uprobe() ? Or that task can be simply preempted before.
Or I missed the point completely?
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