On Sat, 2010-12-25 at 08:11 +1100, Benjamin Herrenschmidt wrote: > On Fri, 2010-12-24 at 00:46 -0500, Steven Rostedt wrote: > > > arch/powerpc/include/asm/irqflags.h | 40 > > ++++++++++++++++++++++++++-------- > > 1 files changed, 30 insertions(+), 10 deletions(-) > > --------------------------- > > commit 5025019505da6731f8be13940bb978617599c935 > > Author: Steven Rostedt <srost...@redhat.com> > > Date: Thu Dec 23 21:07:39 2010 -0800 > > > > powerpc64/tracing: Add frame buffer to calls of trace_hardirqs_on/off > > > > When an interrupt occurs in userspace, we can call > > trace_hardirqs_on/off() > > With one level stack. But if we have irqsoff tracing enabled, > > it checks both CALLER_ADDR0 and CALLER_ADDR1. The second call > > goes two stack frames up. If this is from user space, then there may > > not exist a second stack. > > > > Add a second stack when calling trace_hardirqs_on/off() otherwise > > the following oops might occur: > > Hrm... this is really gross :-) So we add gratuituous overhead because > the code below is dumb :-) What about making the code less stupid > instead when poking at the stack and detect it's coming from userspace > instead ?
Note, when CONFIG_IRQSOFF_TRACE is set, there's already a bit of overhead :-) Anyway, I'll have to take a look at how the frame pointer is set up. Or we could also set up all stacks coming into the kernel to have a "dummy" frame pointer that wont hurt anything if we index into it. Anyway, I'm off till the new year, so I'll worry about it then ;-) -- Steve _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
