Re: [patch V2 28/29] stacktrace: Provide common infrastructure

From: Josh Poimboeuf <jpoimboe@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>,
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Subject: Re: [patch V2 28/29] stacktrace: Provide common infrastructure
Date: Fri, 19 Apr 2019 10:50:44 -0500	[thread overview]
Message-ID: <20190419155044.2uch7eaj4vzg47w6@treble> (raw)
In-Reply-To: <20190419070211.GL4038@hirez.programming.kicks-ass.net>

On Fri, Apr 19, 2019 at 09:02:11AM +0200, Peter Zijlstra wrote:
> On Thu, Apr 18, 2019 at 05:42:55PM +0200, Thomas Gleixner wrote:
> > On Thu, 18 Apr 2019, Josh Poimboeuf wrote:
> 
> > > Another idea I had (but never got a chance to work on) was to extend the
> > > x86 unwind interface to all arches.  So instead of the callbacks, each
> > > arch would implement something like this API:
> 
> > I surely thought about that, but after staring at all incarnations of
> > arch/*/stacktrace.c I just gave up.
> > 
> > Aside of that quite some archs already have callback based unwinders
> > because they use them for more than stacktracing and just have a single
> > implementation of that loop.
> > 
> > I'm fine either way. We can start with x86 and then let archs convert over
> > their stuff, but I wouldn't hold my breath that this will be completed in
> > the forseeable future.
> 
> I suggested the same to Thomas early on, and I even spend the time to
> convert some $random arch to the iterator interface, and while it is
> indeed entirely feasible, it is _far_ more work.
> 
> The callback thing OTOH is flexible enough to do what we want to do now,
> and allows converting most archs to it without too much pain (as Thomas
> said, many archs are already in this form and only need minor API
> adjustments), which gets us in a far better place than we are now.
> 
> And we can always go to iterators later on. But I think getting the
> generic unwinder improved across all archs is a really important first
> step here.

Fair enough.

-- 
Josh