* Thomas Gleixner wrote:
> That would just make the door open for evading lockdep. This has been
> discussed when lockdep was introduced and with a lot of other 'annoying'
> debug features we've seen the same discussion happening.
>
> When they get introduced the number of real issues and false
On Thu, Oct 19, 2017 at 08:21:56PM +, Bart Van Assche wrote:
> * How much review has the Documentation/locking/crossrelease.txt received
> before it went upstream? At least to me that document seems much harder
> to read than other kernel documentation due to weird use of the English
> gr
On Thu, 19 Oct 2017, Bart Van Assche wrote:
> On Thu, 2017-10-19 at 13:33 -0700, Matthew Wilcox wrote:
> > For example, the page lock is not annotatable with lockdep -- we return
> > to userspace with it held, for heaven's sake! So it is quite easy for
> > someone not familiar with the MM locking
On Thu, 19 Oct 2017, Bart Van Assche wrote:
> * How many lock inversion problems have been found so far thanks to the
> cross-release checking? How many false positives have the cross-release
> checks triggered so far? Does the number of real issues that has been
> found outweigh the effort s
On Thu, 2017-10-19 at 13:33 -0700, Matthew Wilcox wrote:
> For example, the page lock is not annotatable with lockdep -- we return
> to userspace with it held, for heaven's sake! So it is quite easy for
> someone not familiar with the MM locking hierarchy to inadvertently
> introduce an ABBA deadl
On Thu, Oct 19, 2017 at 08:21:56PM +, Bart Van Assche wrote:
> In case it wouldn't be clear, your work and the work of others on lockdep
> and preempt-rt is highly appreciated. Sorry that I missed the discussion
> about the cross-release functionality when it went upstream. I have several
> que
On Thu, 2017-10-19 at 21:12 +0200, Thomas Gleixner wrote:
> And just for the record, I wasted enough of my time already to decode 'can
> not happen' dead locks where completions or other wait primitives have been
> involved. I rather spend time annotating stuff after analyzing it proper
> than chas
On Thu, 19 Oct 2017, Thomas Gleixner wrote:
> That's not a lockdep problem and neither can the pure locking dependency
> tracking know that a particular deadlock is not possible by design. It can
> merily record the dependency chains and detect circular dependencies.
>
> There is enough code which
Bart,
On Thu, 19 Oct 2017, Bart Van Assche wrote:
> It seems like you are missing my point.
That might be a perception problem.
> Cross-release checking is really *broken* as a concept. It is impossible
> to improve it to the same reliability level as the kernel v4.13 lockdep
> code. Hence my
On Thu, 2017-10-19 at 17:34 +0200, Thomas Gleixner wrote:
> I really disagree with your reasoning completely
>
> 1) When lockdep was introduced more than ten years ago it was far from
>perfect and we spent a reasonable amount of time to improve it, analyze
>false positives and add the miss
On Thu, 19 Oct 2017, Bart Van Assche wrote:
> On Thu, 2017-10-19 at 14:55 +0900, Byungchul Park wrote:
> > Now the performance regression was fixed, re-enable
> > CONFIG_LOCKDEP_CROSSRELEASE and CONFIG_LOCKDEP_COMPLETIONS.
> >
> > Signed-off-by: Byungchul Park
> > ---
> > lib/Kconfig.debug | 4
On Thu, 2017-10-19 at 14:55 +0900, Byungchul Park wrote:
> Now the performance regression was fixed, re-enable
> CONFIG_LOCKDEP_CROSSRELEASE and CONFIG_LOCKDEP_COMPLETIONS.
>
> Signed-off-by: Byungchul Park
> ---
> lib/Kconfig.debug | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
Now the performance regression was fixed, re-enable
CONFIG_LOCKDEP_CROSSRELEASE and CONFIG_LOCKDEP_COMPLETIONS.
Signed-off-by: Byungchul Park
---
lib/Kconfig.debug | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 90ea784..fe8fceb
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