linux-kernel - Re: [PATCH v5 3.1.0-rc4-tip 26/26] uprobes: queue signals while thread is singlestepping.

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Message-ID: <20110927131213.GE3685@linux.vnet.ibm.com>
Date:	Tue, 27 Sep 2011 18:42:13 +0530
From:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Ingo Molnar <mingo@...e.hu>, Steven Rostedt <rostedt@...dmis.org>,
	Linux-mm <linux-mm@...ck.org>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Hugh Dickins <hughd@...gle.com>,
	Christoph Hellwig <hch@...radead.org>,
	Andi Kleen <andi@...stfloor.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Jonathan Corbet <corbet@....net>,
	Oleg Nesterov <oleg@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jim Keniston <jkenisto@...ux.vnet.ibm.com>,
	Roland McGrath <roland@...k.frob.com>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 3.1.0-rc4-tip 26/26]   uprobes: queue signals while
 thread is singlestepping.

* Peter Zijlstra <peterz@...radead.org> [2011-09-27 15:03:46]:

> On Tue, 2011-09-20 at 17:35 +0530, Srikar Dronamraju wrote:
> > +#ifdef CONFIG_UPROBES
> > +       if (!group && t->utask && t->utask->active_uprobe)
> > +               pending = &t->utask->delayed;
> > +#endif
> > +
> >         /*
> >          * Short-circuit ignored signals and support queuing
> >          * exactly one non-rt signal, so that we can get more
> > @@ -1106,6 +1111,11 @@ static int __send_signal(int sig, struct siginfo *info, struct task_struct *t,
> >                 }
> >         }
> >  
> > +#ifdef CONFIG_UPROBES
> > +       if (!group && t->utask && t->utask->active_uprobe)
> > +               return 0;
> > +#endif
> > +
> >  out_set:
> >         signalfd_notify(t, sig);
> >         sigaddset(&pending->signal, sig);
> > @@ -1569,6 +1579,13 @@ int send_sigqueue(struct sigqueue *q, struct task_struct *t, int group)
> >         }
> >         q->info.si_overrun = 0;
> >  
> > +#ifdef CONFIG_UPROBES
> > +       if (!group && t->utask && t->utask->active_uprobe) {
> > +               pending = &t->utask->delayed;
> > +               list_add_tail(&q->list, &pending->list);
> > +               goto out;
> > +       }
> > +#endif
> >         signalfd_notify(t, sig);
> >         pending = group ? &t->signal->shared_pending : &t->pending;
> >         list_add_tail(&q->list, &pending->list);
> > @@ -2199,7 +2216,10 @@ int get_signal_to_deliver(siginfo_t *info, struct k_sigaction *return_ka,
> >                         spin_unlock_irq(&sighand->siglock);
> >                         goto relock;
> >                 }
> > -
> > +#ifdef CONFIG_UPROBES
> > +               if (current->utask && current->utask->active_uprobe)
> > +                       break;
> > +#endif 
> 
> That's just crying for something like:
> 
> #ifdef CONFIG_UPROBES
> static inline bool uprobe_delay_signal(struct task_struct *p)
> {
> 	return p->utask && p->utask->active_uprobe;
> }
> #else
> static inline bool uprobe_delay_signal(struct task_struct *p)
> {
> 	return false;
> }
> #endif
> 
> That'll instantly kill the #ifdeffery as well as describe wtf you're
> actually doing.


Okay, 

I did a rethink and implemented this patch a little differently using
block_all_signals, unblock_all_signals. This wouldnt need the 
#ifdeffery + no changes in kernel/signal.c

Will post the same in the next patchset.

-- 
Thanks and Regards
Srikar
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