2012/9/25 Michael Neuling <mi...@neuling.org>: > Michael Neuling <mi...@neuling.org> wrote: > >> Frederic Weisbecker <fweis...@gmail.com> wrote: >> >> > On Thu, Aug 16, 2012 at 02:23:54PM +1000, Michael Neuling wrote: >> > > Hi, >> > > >> > > I've been trying to get hardware breakpoints with perf to work on POWER7 >> > > but I'm getting the following: >> > > >> > > % perf record -e mem:0x10000000 true >> > > >> > > Error: sys_perf_event_open() syscall returned with 28 (No space left >> > > on device). /bin/dmesg may provide additional information. >> > > >> > > Fatal: No CONFIG_PERF_EVENTS=y kernel support configured? >> > > >> > > true: Terminated >> > > >> > > (FWIW adding -a and it works fine) >> > > >> > > Debugging it seems that __reserve_bp_slot() is returning ENOSPC because >> > > it thinks there are no free breakpoint slots on this CPU. >> > > >> > > I have a 2 CPUs, so perf userspace is doing two perf_event_open syscalls >> > > to add a counter to each CPU [1]. The first syscall succeeds but the >> > > second is failing. >> > > >> > > On this second syscall, fetch_bp_busy_slots() sets slots.pinned to be 1, >> > > despite there being no breakpoint on this CPU. This is because the call >> > > the task_bp_pinned, checks all CPUs, rather than just the current CPU. >> > > POWER7 only has one hardware breakpoint per CPU (ie. HBP_NUM=1), so we >> > > return ENOSPC. >> > > >> > > The following patch fixes this by checking the associated CPU for each >> > > breakpoint in task_bp_pinned. I'm not familiar with this code, so it's >> > > provided as a reference to the above issue. >> > > >> > > Mikey >> > > >> > > 1. not sure why it doesn't just do one syscall and specify all CPUs, but >> > > that's another issue. Using two syscalls should work. >> > >> > This patch seems to make sense. I'll try it and run some tests. >> > Can I have your Signed-off-by ? > > Frederic, > > Did you ever get to testing or integrating this patch? > > Mikey
Sorry, I forgot this in my mailbox. I'm going to look at this in the next few days. Feel free to harass me by email or IRC if I don't give news on this soon. _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
