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From: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
To: Andrew Morton <akpm@osdl.org>
Cc: Ingo Molnar <mingo@redhat.com>,
	Greg Kroah-Hartman <gregkh@suse.de>,
	Christoph Hellwig <hch@infradead.org>,
	linux-kernel@vger.kernel.org, ltt-dev@shafik.org,
	"Martin J. Bligh" <mbligh@mbligh.org>,
	Douglas Niehaus <niehaus@eecs.ku.edu>,
	systemtap@sources.redhat.com,
	Thomas Gleixner <tglx@linutronix.de>,
	Richard J Moore <richardj_moore@uk.ibm.com>
Subject: Re: [PATCH 2/2] lockdep reentrancy
Date: Wed, 24 Jan 2007 11:55:00 -0500	[thread overview]
Message-ID: <20070124165500.GD4979@Krystal> (raw)
In-Reply-To: <20070123202909.6b7dcd17.akpm@osdl.org>

Hi Andrew,

* Andrew Morton (akpm@osdl.org) wrote:
> On Tue, 16 Jan 2007 12:56:31 -0500
> Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> wrote:
> 
> > Here is a patch to lockdep.c so it behaves correctly when a kprobe breakpoint is
> > put on a marker within hardirq tracing functions as long as the marker is within
> > the lockdep_recursion incremented boundaries. It should apply on 
> > 2.6.20-rc4-git3.
> > 
> > Mathieu
> > 
> > Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
> > 
> > 
> > @@ -1841,33 +1843,36 @@ void trace_hardirqs_on(void)
> 
> You lost the patch headers.
> 
> >  	struct task_struct *curr = current;
> >  	unsigned long ip;
> >  
> >  	if (unlikely(!debug_locks || current->lockdep_recursion))
> >  		return;
> >  
> > +	current->lockdep_recursion++;
> > +	barrier();
> 
> Why can't we use lockdep_off() here?
> 

Because I thought that changing lockdep_off() for the whole system might be a
little different than adding a lockdep recursion protection. See my other email
for the lockdep_on/off() discussion.

And please drop this patch : It sometimes make lockdep trigger false positives
under heavy IRQ load because of a dropped lockdep event.

Mathieu


> >  	if (DEBUG_LOCKS_WARN_ON(unlikely(!early_boot_irqs_enabled)))
> > -		return;
> > +		goto end;
> >  
> >  	if (unlikely(curr->hardirqs_enabled)) {
> >  		debug_atomic_inc(&redundant_hardirqs_on);
> > -		return;
> > +		goto end;
> >  	}
> >  	/* we'll do an OFF -> ON transition: */
> >  	curr->hardirqs_enabled = 1;
> >  	ip = (unsigned long) __builtin_return_address(0);
> >  
> >  	if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
> > -		return;
> > +		goto end;
> >  	if (DEBUG_LOCKS_WARN_ON(current->hardirq_context))
> > -		return;
> > +		goto end;
> >  	/*
> >  	 * We are going to turn hardirqs on, so set the
> >  	 * usage bit for all held locks:
> >  	 */
> >  	if (!mark_held_locks(curr, 1, ip))
> > -		return;
> > +		goto end;
> >  	/*
> >  	 * If we have softirqs enabled, then set the usage
> >  	 * bit for all held locks. (disabled hardirqs prevented
> > @@ -1875,11 +1880,14 @@ void trace_hardirqs_on(void)
> >  	 */
> >  	if (curr->softirqs_enabled)
> >  		if (!mark_held_locks(curr, 0, ip))
> > -			return;
> > +			goto end;
> >  
> >  	curr->hardirq_enable_ip = ip;
> >  	curr->hardirq_enable_event = ++curr->irq_events;
> >  	debug_atomic_inc(&hardirqs_on_events);
> > +end:
> > +	barrier();
> > +	current->lockdep_recursion--;
> 
> lockdep_on()?
> 
> >  }
> >  
> >  EXPORT_SYMBOL(trace_hardirqs_on);
> > @@ -1888,14 +1896,17 @@ void trace_hardirqs_off(void)
> >  {
> >  	struct task_struct *curr = current;
> >  
> >  	if (unlikely(!debug_locks || current->lockdep_recursion))
> >  		return;
> >  
> > +	current->lockdep_recursion++;
> > +	barrier();
> 
> lockdep_off()?
> 
> >  	if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
> > -		return;
> > +		goto end;
> >  
> >  	if (curr->hardirqs_enabled) {
> >  		/*
> > @@ -1910,6 +1921,9 @@ void trace_hardirqs_off(void)
> >  		debug_atomic_inc(&hardirqs_off_events);
> >  	} else
> >  		debug_atomic_inc(&redundant_hardirqs_off);
> > +end:
> > +	barrier();
> > +	current->lockdep_recursion--;
> 
> lockdep_on()?

-- 
OpenPGP public key:              http://krystal.dyndns.org:8080/key/compudj.gpg
Key fingerprint:     8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68 

      reply	other threads:[~2007-01-24 16:55 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2006-12-20 23:52 [PATCH 0/4] Linux Kernel Markers Mathieu Desnoyers
2006-12-20 23:57 ` [PATCH 1/4] Linux Kernel Markers : Architecture agnostic code Mathieu Desnoyers
2006-12-20 23:59 ` [PATCH 2/4] Linux Kernel Markers : kconfig menus Mathieu Desnoyers
2006-12-21  0:00 ` [PATCH 3/4] Linux Kernel Markers : i386 optimisation Mathieu Desnoyers
2006-12-21  0:01 ` [PATCH 4/4] Linux Kernel Markers : powerpc optimisation Mathieu Desnoyers
2007-01-13  1:33 ` [PATCH 0/4] Linux Kernel Markers Richard J Moore
2007-01-13  5:45   ` Mathieu Desnoyers
2007-01-16 17:41     ` [PATCH 0/4 update] Linux Kernel Markers - i386 : pIII erratum 49 : XMC Mathieu Desnoyers
2007-01-16 18:35       ` Frank Ch. Eigler
2007-01-16 21:27       ` [PATCH 0/4 update] kprobes and traps Mathieu Desnoyers
2007-01-17 12:25         ` S. P. Prasanna
2007-01-16 17:56   ` [PATCH 1/2] lockdep missing barrier() Mathieu Desnoyers
2007-01-24  4:26     ` Andrew Morton
2007-01-24 16:51       ` Mathieu Desnoyers
2007-01-24 17:24         ` [PATCH] order of lockdep off/on in vprintk() should be changed Mathieu Desnoyers
2007-01-24 17:55           ` [PATCH] minimize lockdep_on/off side-effect Mathieu Desnoyers
2007-01-16 17:56   ` [PATCH 2/2] lockdep reentrancy Mathieu Desnoyers
2007-01-24  4:29     ` Andrew Morton
2007-01-24 16:55       ` Mathieu Desnoyers [this message]

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