On 11/05/15 18:41, Thomas Meyer wrote: > Am 11.05.2015 7:31 nachm. schrieb Anton Ivanov > <anton.iva...@kot-begemot.co.uk>: >> On 11/05/15 18:20, Anton Ivanov wrote: >>> On 11/05/15 18:00, Thomas Meyer wrote: >>>> Hi, >>>> >>>> maybe there is a bug in how the timers are created for all user space >>>> processes. >>>> In the latest patch I use os__timer_remain for the initial interval. >>>> The idea was to launch all timers at the same time. But I now think this >>>> can never work using relative times, especially when os__timer_remain >>>> returns 0, then the new timer is never launched. >>> That is not a bad idea, just requires a more complex check in setting up >>> interval so it is reset to default when a zero value or value > HZ is >>> passed. >>> >>> >>>> That may explain the hangs you see. >>>> You could try to replace os__timer_remain with the current HZ value >>>> in nanoseconds. >>> I am going to adjust time.c instead as above. >> Both approaches fail - the check (that is expected actually, I did not >> think properly here - it does not cover the stub in kernel/skas) and the >> setting of data to the correct initial values. >> >> Also, if it was just not starting timers it would have been possible to >> beat the process with USR2 on the head until its morale improves. Well, >> "while true; do kill -USR2 PID ; done" does not change the behavior, it >> still hangs and is still possible to terminate the errant process by >> sending SIGSEGV to the UML thread which is shown as 100% CPU and in R state. > Yes, sending USR2 should do the same. Correct. > >> Problem is somewhere else. I am surprised it worked correctly in the >> original one as there for 100% flat CPU usage it should have converged >> to a behavior which is similar to what we have now. > Mhh. Strange. Any hints how I can reproduce this? > > I need to see the same behaviour, i.e. the hang on my machine to begin to > understand what is going on here.
Start off with a Debian image of let's say wheezy and hit it with a dist-upgrade to the next release. This produces enough IO+CPU at the same time to trigger it. I get it 100% reproducible every time it tries to unpack the first couple of packages. I tried to trigger backtraces but could not get anything informative. The old trick of hitting the kernel with SIGILL which worked very nicely in older kernel versions no longer works :( > > Thanks for testing Anton. I wish I had more time at the moment to debug it and fix it :( We are nearly there and it is worth it. A. > > >> A. >> >>> A. >>> >>>> Kind regards >>>> Thomad >>>> >>>> A >>> [snip] >>> >>> A. >>> >>> ------------------------------------------------------------------------------ >>> One dashboard for servers and applications across Physical-Virtual-Cloud >>> Widest out-of-the-box monitoring support with 50+ applications >>> Performance metrics, stats and reports that give you Actionable Insights >>> Deep dive visibility with transaction tracing using APM Insight. >>> http://ad.doubleclick.net/ddm/clk/290420510;117567292;y >>> _______________________________________________ >>> User-mode-linux-devel mailing list >>> User-mode-linux-devel@lists.sourceforge.net >>> https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel >>> >> >> ------------------------------------------------------------------------------ >> One dashboard for servers and applications across Physical-Virtual-Cloud >> Widest out-of-the-box monitoring support with 50+ applications >> Performance metrics, stats and reports that give you Actionable Insights >> Deep dive visibility with transaction tracing using APM Insight. >> http://ad.doubleclick.net/ddm/clk/290420510;117567292;y >> _______________________________________________ >> User-mode-linux-devel mailing list >> User-mode-linux-devel@lists.sourceforge.net >> https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel ------------------------------------------------------------------------------ One dashboard for servers and applications across Physical-Virtual-Cloud Widest out-of-the-box monitoring support with 50+ applications Performance metrics, stats and reports that give you Actionable Insights Deep dive visibility with transaction tracing using APM Insight. http://ad.doubleclick.net/ddm/clk/290420510;117567292;y _______________________________________________ User-mode-linux-devel mailing list User-mode-linux-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel
