On Mon, Dec 20, 2010 at 10:07:14PM +0100, Sedat Dilek wrote: > Hi Nick, > > after upgrading my toolchain and kernel-buildsystem I found some time > spending in getting some more infos on the systemd w/ vfs-scale > problem. > Eric reported in [1] same problems as I have seen. > > My systemd is now v15+git20101210.8a9ef77 and Linux kernel is: > > # cat /proc/version > Linux version 2.6.37-rc6-686 (Debian > 2.6.37~rc6-5~next20101220.dileks.1) (sedat.dilek@xxxxxxxxx) (gcc > version 4.5.2 (Debian 4.5.2-1) ) #1 SMP Mon Dec 20 19:03:29 CET 2010 > > I could take some new pics [2]. > > [3] shows a kernel NULL pointer dereference (dmesg command in > kdb-console), but the address is not displayed, might be I need to set > some additional kernel-debug-options. > > [4] shows the output of "btp 4" (backtrace PID #4 from kdb-console), > see also in [3] "*pde = 00000000" (8 zeroes) shows <4> (PID #4) at the > beginning of the line. > > I have also a "btp 1" (systemd has PID #1). > > Hope this helps to narrow down the problem. > If you need additional informations or (disasm-ed) files, please let me know. > > Some pics are doubled, sorry for the bad quality, I won't be a surgery > (need a calm hand, turned off auto-flash of my digicam is the real > cause I guess ;-)). Thanks to you both for testing and reporting this. The important part is NULL instruction pointer at dput. I have a patch to set various d_flags according to what d_op functions have been defined. This allows branch and cacheline load reduction in common cases in fastpaths. However those flags were set but not cleared, not expecting d_ops to be switched on active dentries. cgroups filesystem actually switches from simple dentry ops to its own one, when turning from a negative to positive dentry. That's possibly OK technically (although I didn't consider all races), but AFAIKS it is not something that a filesystem is allowed to "know". I'll submit a patch to fix cgroups, and a bugcheck to catch such things again. Thanks, Nick -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
