Corey, I looked at the pfm_handle_work() code. Normally this functions gets called only if the TIF_PERFMON_WORK flag is set. On Power, it seems the logic is coded differently. You call systematically and in pfm_handle_work() you check the flag, and if not set you return.
During boot, I don't expect TIF_PERFMON_WORK to be set. So I don't understand why FTRACER would have a problem with a function that does a simple test and returns. On Thu, Dec 18, 2008 at 9:04 AM, Corey Ashford <cjash...@linux.vnet.ibm.com> wrote: > Hi Stephane and Paul, > > After comparing sources, I didn't find any remarkable differences > between the two (bare 2.6.28-rc6 and Stephane's perfmon2-enhanced > 2.6.28-rc6) > > It didn't immediately occur to me that I could hit SysRq when the system > hung, so I decided to give that a try, and I did get a stack trace, showing: > pc = ._mcount + 0x1c > lr = .pfm_handle_work + 0x30 > > The stack trace showed that rc.sysinit called into the kernel for some > service (I'm not sure what service at this point), and on its way out > again, it made a call to pfm_handle_work, which then calls _mcount. > Looking at the source, pfm_handle_work doesn't call _mcount explicitly. > > It appears that this _mcount function is used for kernel function > tracing, and by default (via arch/powerpc/pseriesdefconfig) the > CONFIG_FUNCTION_TRACER feature is turned on. It also appears that this > is an area of code that's changed between fairly recent SLES kernels > (beta), and 2.6.28-rc6, because the CONFIG variables are named differently. > > As an experiment, I disabled CONFIG_FUNCTION_TRACE, re-built the kernel, > and it booted successfully. > > So there's something in pfm_handle_work that is confusing the function > trace code, at least on Power. Paul, do you know what might be causing > this problem? > > In any case, if you need a short term work-around, this appears to be > the way to do it - turn off CONFIG_FUNCTION_TRACER. > > > Regards, > > - Corey > > Corey Ashford > Software Engineer > IBM Linux Technology Center, Linux Toolchain > Beaverton, OR > 503-578-3507 > cjash...@us.ibm.com > > > Corey Ashford wrote: >> I want to report that perfmon2 in 2.6.28-rc6 is broken somehow on >> Power6, and possibly all Power-based machines. >> >> Today, I tried booting Stephane's 2.6.28-rc6 perfmon2 kernel with >> perfmon2 enabled, and it hangs during the boot-up process right after >> outputting the line "INIT: version 2.86 booting" >> >> Without perfmon2 enabled, it boots up fine. >> >> So something has regressed, and I'm not sure what. I will see if I can >> find the culprit and submit a patch. >> >> Regards, >> >> - Corey >> >> Corey Ashford >> Software Engineer >> IBM Linux Technology Center, Linux Toolchain >> Beaverton, OR >> 503-578-3507 >> cjash...@us.ibm.com >> >> >> >> >> ------------------------------------------------------------------------------ >> SF.Net email is Sponsored by MIX09, March 18-20, 2009 in Las Vegas, Nevada. >> The future of the web can't happen without you. Join us at MIX09 to help >> pave the way to the Next Web now. Learn more and register at >> http://ad.doubleclick.net/clk;208669438;13503038;i?http://2009.visitmix.com/ >> _______________________________________________ >> perfmon2-devel mailing list >> perfmon2-devel@lists.sourceforge.net >> https://lists.sourceforge.net/lists/listinfo/perfmon2-devel > > > > ------------------------------------------------------------------------------ > SF.Net email is Sponsored by MIX09, March 18-20, 2009 in Las Vegas, Nevada. > The future of the web can't happen without you. Join us at MIX09 to help > pave the way to the Next Web now. Learn more and register at > http://ad.doubleclick.net/clk;208669438;13503038;i?http://2009.visitmix.com/ > _______________________________________________ > perfmon2-devel mailing list > perfmon2-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/perfmon2-devel > ------------------------------------------------------------------------------ SF.Net email is Sponsored by MIX09, March 18-20, 2009 in Las Vegas, Nevada. The future of the web can't happen without you. Join us at MIX09 to help pave the way to the Next Web now. Learn more and register at http://ad.doubleclick.net/clk;208669438;13503038;i?http://2009.visitmix.com/ _______________________________________________ perfmon2-devel mailing list perfmon2-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/perfmon2-devel
