On Sat, 2014-05-03 at 18:35 +0200, Dirk Behme wrote: > Am 02.05.2014 20:09, schrieb Kamal Mostafa: > > On Fri, 2014-05-02 at 13:30 -0400, gregkh wrote: > >> On Fri, May 02, 2014 at 10:07:33AM -0700, Kamal Mostafa wrote: > >>> Dirk Behme points out that this "Cc: stable" commit breaks the > >>> lttng-modules userspace API when applied to stable kernels. Stable > >>> versions 3.2, 3.8, 3.11, and 3.13 (at least) have all queued it: > >>> > >>> af5040da01ef980670b3741b3e10733ee3e33566 > >>> blktrace: fix accounting of partially completed requests > >>> > >>> > >>> On Thu, 2014-05-01 at 10:28 +0200, Dirk Behme wrote: > >>>> [...] might break the build of the user space lttng-modules > >>>> (lttng-probe-block.c) due the the API change of > >>>> trace_block_rq_complete(). > >>> > >>>> [...] On the other hand, looking into the lttng-modules git > >>>> http://git.lttng.org/?p=lttng-modules.git;a=commitdiff;h=1c53e689434a6bdd7dc3f54c07bfb72750d1d24c > >>>> looks like this is the necessary user space adaption to the kernel > >>>> change? So this looks like that lttng-modules expects a KERNEL_VERSION > >>>>> = (3,15,0) to have this commit? > >>> > >>> > >>> My inclination is that we probably need to revert/drop "af5040d > >>> blktrace: fix accounting..." from the stable kernels to unbreak the > >>> userspace API. > >> > >> Then you will run into this issue with 3.15, when it is released. > > > > No, I think "#if (LINUX_VERSION_CODE >= KERNEL_VERSION(3,15,0))" in the > > lttng-modules commit referenced above guards against that. Apparently, > > lttng-modules expects to see the new API in >= 3.15 and the old API in > > the stable kernels. > > I'm not in the position to judge if it's a lttng or a kernel community > issue ;) > > So just for my understanding: > > Having > > #if (LINUX_VERSION_CODE >= KERNEL_VERSION(3,15,0)) > > in lttng-modules commit > > http://git.lttng.org/?p=lttng-modules.git;a=commitdiff;h=1c53e689434a6bdd7dc3f54c07bfb72750d1d24c > > does mean that we don't have a lttng-modules version which will build > against the -stable kernels (3.2.58, 3,8.13.22 etc) with the back > ported commit [1], atm? [...] I don't understand why lttng-modules has its own definitions of tracepoints. However, I suspect that it doesn't use anything beyond the event structure definition, which has *not* changed, making that commit a no-op. Someone who cares should actually experiment with using old lttng-modules with blktrace eventsf rom a patched kernel. Ben. -- Ben Hutchings All the simple programs have been written, and all the good names taken.
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