This is a reply to a thread from back in Nov 2016...
Linus> The thing is, with function tracing, you *can* get the return value
Linus> and arguments. Sure, you'll probably need to write eBPF and just
Linus> attach it to that fentry call point, and yes, if something is inlined
Linus> you're just sc
On Mon, Nov 28, 2016 at 03:46:51PM -0700, Ross Zwisler wrote:
> On Fri, Nov 25, 2016 at 02:00:59PM +1100, Dave Chinner wrote:
> > On Wed, Nov 23, 2016 at 11:44:19AM -0700, Ross Zwisler wrote:
> > > Tracepoints are the standard way to capture debugging and tracing
> > > information in many parts of
On Fri, Nov 25, 2016 at 02:00:59PM +1100, Dave Chinner wrote:
> On Wed, Nov 23, 2016 at 11:44:19AM -0700, Ross Zwisler wrote:
> > Tracepoints are the standard way to capture debugging and tracing
> > information in many parts of the kernel, including the XFS and ext4
> > filesystems. Create a trac
On Sun, Nov 27, 2016 at 04:58:43PM -0800, Linus Torvalds wrote:
> On Sun, Nov 27, 2016 at 2:42 PM, Dave Chinner wrote:
> >
> > And that's exactly why we need a method of marking tracepoints as
> > stable. How else are we going to know whether a specific tracepoint
> > is stable if the kernel code
On Fri 25-11-16 16:48:40, Ted Tso wrote:
> On Fri, Nov 25, 2016 at 11:51:26AM -0800, Linus Torvalds wrote:
> > We do have filesystem code that is just disgusting. As an example:
> > fs/afs/ tends to have these crazy "_enter()/_exit()" macros in every
> > single function. If you want that, use the f
On Sun, Nov 27, 2016 at 04:58:43PM -0800, Linus Torvalds wrote:
> You are living in some unrealistic dream-world where you think you can
> get the right tracepoint on the first try.
>
> So there is no way in hell I would ever mark any tracepoint "stable"
> until it has had a fair amount of use, an
On Sun, Nov 27, 2016 at 2:42 PM, Dave Chinner wrote:
>
> And that's exactly why we need a method of marking tracepoints as
> stable. How else are we going to know whether a specific tracepoint
> is stable if the kernel code doesn't document that it's stable?
You are living in some unrealistic dre
On Fri, Nov 25, 2016 at 11:51:26AM -0800, Linus Torvalds wrote:
> On Thu, Nov 24, 2016 at 11:37 PM, Al Viro wrote:
> >
> > My impression is that nobody (at least kernel-side) wants them to be
> > a stable ABI, so long as nobody in userland screams about their code
> > being broken, everything is f
On Fri, Nov 25, 2016 at 1:48 PM, Theodore Ts'o wrote:
>
> There is a reason why people want to be able to do that, and that's
> because kprobes doesn't give you access to the arguments and return
> codes to the functions.
Honestly, that's simply not a good reason.
What if everybody did this? Do
On Fri, Nov 25, 2016 at 11:51:26AM -0800, Linus Torvalds wrote:
> We do have filesystem code that is just disgusting. As an example:
> fs/afs/ tends to have these crazy "_enter()/_exit()" macros in every
> single function. If you want that, use the function tracer. That seems
> to be just debugging
> We do have filesystem code that is just disgusting. As an example:
> fs/afs/ tends to have these crazy "_enter()/_exit()" macros in every
> single function.
Hmmm... we have "gossip" statements in Orangefs which can be triggered with
a debugfs knob... lots of functions have a gossip statement at
On Thu, Nov 24, 2016 at 11:37 PM, Al Viro wrote:
>
> My impression is that nobody (at least kernel-side) wants them to be
> a stable ABI, so long as nobody in userland screams about their code
> being broken, everything is fine. As usual, if nobody notices an ABI
> change, it hasn't happened. Th
On Fri, Nov 25, 2016 at 06:06:42PM +1100, Dave Chinner wrote:
> > Tell that to Linus. You had been in the room, IIRC, when that had been
> > brought up this year in Santa Fe.
>
> No, I wasn't at KS or plumbers, so this is all news to me.
Sorry, thought you had been at KS ;-/ My apologies...
[
On Fri, Nov 25, 2016 at 04:14:19AM +, Al Viro wrote:
> [Linus Cc'd]
>
> On Fri, Nov 25, 2016 at 01:49:18PM +1100, Dave Chinner wrote:
> > > they have become parts of stable userland ABI and are to be maintained
> > > indefinitely. Don't expect "tracepoints are special case" to prevent
> > >
[Linus Cc'd]
On Fri, Nov 25, 2016 at 01:49:18PM +1100, Dave Chinner wrote:
> > they have become parts of stable userland ABI and are to be maintained
> > indefinitely. Don't expect "tracepoints are special case" to prevent that.
>
> I call bullshit just like I always do when someone spouts this
On Wed, Nov 23, 2016 at 11:44:19AM -0700, Ross Zwisler wrote:
> Tracepoints are the standard way to capture debugging and tracing
> information in many parts of the kernel, including the XFS and ext4
> filesystems. Create a tracepoint header for FS DAX and add the first DAX
> tracepoints to the PM
On Thu, Nov 24, 2016 at 05:32:20PM +, Al Viro wrote:
> On Wed, Nov 23, 2016 at 11:44:19AM -0700, Ross Zwisler wrote:
> > Tracepoints are the standard way to capture debugging and tracing
> > information in many parts of the kernel, including the XFS and ext4
> > filesystems. Create a tracepoin
On Wed, Nov 23, 2016 at 11:44:19AM -0700, Ross Zwisler wrote:
> Tracepoints are the standard way to capture debugging and tracing
> information in many parts of the kernel, including the XFS and ext4
> filesystems. Create a tracepoint header for FS DAX and add the first DAX
> tracepoints to the PM
On Wed 23-11-16 11:44:19, Ross Zwisler wrote:
> Tracepoints are the standard way to capture debugging and tracing
> information in many parts of the kernel, including the XFS and ext4
> filesystems. Create a tracepoint header for FS DAX and add the first DAX
> tracepoints to the PMD fault handler.
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