On Mon, 2015-08-31 at 18:06 +1000, Dave Chinner wrote: > On Wed, Mar 11, 2015 at 10:13:56PM -0500, Scott Wood wrote: > > Use %pS for actual addresses, otherwise you'll get bad output > > on arches like ppc64 where %pF expects a function descriptor. > > > > Signed-off-by: Scott Wood <[email protected]> > > Cc: [email protected] > > Scott, I've just found that this change (commit 65dd297 "xfs: %pF is > only for function pointers") breaks the symbolic printing in XFS > trace events on x86_64. eg. > > > diff --git a/fs/xfs/xfs_trace.h b/fs/xfs/xfs_trace.h > > index 51372e3..b5ac81e 100644 > > --- a/fs/xfs/xfs_trace.h > > +++ b/fs/xfs/xfs_trace.h > > @@ -115,7 +115,7 @@ DECLARE_EVENT_CLASS(xfs_perag_class, > > __entry->refcount = refcount; > > __entry->caller_ip = caller_ip; > > ), > > - TP_printk("dev %d:%d agno %u refcount %d caller %pf", > > + TP_printk("dev %d:%d agno %u refcount %d caller %ps", > > MAJOR(__entry->dev), MINOR(__entry->dev), > > __entry->agno, > > __entry->refcount, > > This results in output like this: > > 760.828474: xfs_perag_get: dev 253:32 agno 13 refcount 10 caller > 0xffffffff814eef02s > 760.828476: xfs_perag_put: dev 253:32 agno 13 refcount 9 caller > 0xffffffff814eefe8s > > When I revert this commit, I get: > > 71.911265: xfs_perag_get: dev 253:32 agno 0 refcount 11 caller > xfs_extent_busy_insert > 71.911266: xfs_perag_put: dev 253:32 agno 0 refcount 10 caller > xfs_extent_busy_insert > > Which is exactly what we should be getting from the tracing. I'm > using trace-cmd to gather and print the events, and it breaks > both old and current versions of trace-cmd. > > Can you please look into why this change broke the tracing output > on x86-64 - if there is no obvious/easy fix for it, then I'm simply > going to revert it because having the tracing work correctly on > x86-64 is far more important to us than ppc64 or ia64....
It looks like the cause is that TP_printk() is not really printk() -- it actually passes the format to userspace which has its own, not 100% compatible implementation pretty_print() in tools/lib/traceevent/event- parse.c. %pf in that function behaves like %ps in the kernel, and %ps is absent. -Scott -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
