On Thu, 2009-03-19 at 23:23 +0100, Miklos Szeredi wrote: > From: Miklos Szeredi <mszer...@suse.cz> > > This patch fixes bug #12208. > > This turned out to be not a scheduler regression, but an already > existing problem in ptrace being triggered by subtle scheduler > changes. > > The problem is this: > > - task A is ptracing task B > - task B stops on a trace event > - task A is woken up and preempts task B > - task A calls ptrace on task B, which does ptrace_check_attach() > - this calls wait_task_inactive(), which sees that task B is still on the > runq > - task A goes to sleep for a jiffy > - ... > > Since UML does lots of the above sequences, those jiffies quickly add > up to make it slow as hell. > > This patch solves this by not scheduling on preempt_enable() after > ptrace_stop() has woken up the tracer.
Nice,.. however did you find this? Ingo is looking at changing wait_task_inactive() to not be quite so stupid. I'll let him respond with more details when he's done poking at the code :-) ------------------------------------------------------------------------------ Apps built with the Adobe(R) Flex(R) framework and Flex Builder(TM) are powering Web 2.0 with engaging, cross-platform capabilities. Quickly and easily build your RIAs with Flex Builder, the Eclipse(TM)based development software that enables intelligent coding and step-through debugging. Download the free 60 day trial. http://p.sf.net/sfu/www-adobe-com _______________________________________________ User-mode-linux-devel mailing list User-mode-linux-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel
