On Mon, May 25, 2015 at 01:05:15PM +0300, Kirill A. Shutemov wrote: > On Sun, May 24, 2015 at 09:34:04PM +0200, Christoffer Dall wrote: > > Hi all, > > > > I noticed a regression on my arm64 APM X-Gene system a couple > > of weeks back. I would occassionally see the system lock up and see RCU > > stalls during the caching phase of kernbench. I then wrote a small > > script that does nothing but cache the files > > (http://paste.ubuntu.com/11324767/) and ran that in a loop. On a known > > bad commit (v4.1-rc2), out of 25 boots, I never saw it get past 21 > > iterations of the loop. I have since tried to run a bisect from v3.19 to > > v4.0 using 100 iterations as my criteria for a good commit. > > > > This resulted in the following first bad commit: > > > > 10359213d05acf804558bda7cc9b8422a828d1cd > > (mm: incorporate read-only pages into transparent huge pages, 2015-02-11) > > > > Indeed, running the workload on v4.1-rc4 still produced the behavior, > > but reverting the above commit gets me through 100 iterations of the > > loop. > > > > I have not tried to reproduce on an x86 system. Turning on a bunch > > of kernel debugging features *seems* to hide the problem. My config for > > the XGene system is defconfig + CONFIG_BRIDGE and > > CONFIG_POWER_RESET_XGENE. > > > > Please let me know if I can help test patches or other things I can > > do to help. I'm afraid that by simply reading the patch I didn't see > > anything obviously wrong with it which would cause this behavior. > > I don't see the problem on x86. I'm wondering if we could have some weird combination of how the specific architecture works along with these patches... > > Some backtraces could help to track it down. > I don't really get backtraces as the sytem just locks up. But here are some of the RCU stalls as I've observed them on the console: http://paste.ubuntu.com/11014701/ http://paste.ubuntu.com/11023143/ http://paste.ubuntu.com/11023261/ Occasionally, I also get this error from the SATA system at the moment when I power off the device, but not sure if it is related: ata1: exception Emask 0x10 SAct 0x0 SErr 0x180000 action 0xe frozen ata1: irq_stat 0x00400000, PHY RDY changed ata1: SError: { 10B8B Dispar } Thanks, -Christoffer -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>