On Wed, May 18, 2016 at 01:29:55AM -0400, Jerrin Shaji George wrote: > Hi Greg, > > Thanks for your response. > > On Tue, May 17, 2016 at 7:20 PM, Greg KH <greg@xxxxxxxxx> wrote: > > On Tue, May 17, 2016 at 06:55:07PM -0400, Jerrin Shaji George wrote: > >> Hi All, > >> > >> I wanted help with a piece of code that I have been working on. > >> > >> Please see - > >> > >> https://gist.github.com/jerrinsg/333e584d1f65dc95b9f13b61dcebdaa7 > >> > >> I have written two function, migrate_to and migrate_back. migrate_to is used > >> to remove a process from the run queue, and migrate_back is used to insert this > >> process back into the run queue. > >> > >> The gist is from a taken from a larger project, where we are working on building > >> a mechanism to support thread migration across heterogeneous processors. > >> migrate_to_call() will be called by a thread which wants to remove itself from > >> the run queue (hence, it will pass the current task struct as the migration > >> argument). Once the other processor completes execution of the assigned task, it > >> will interrupt the main processor, which runs an interrupt handler, which in > >> turn calls the migrate_back_call() function. It passes the task struct of the > >> process that was removed from the run queue earlier to this function. > >> > >> This mechanism works fine the first few times, but when this process is repeated > >> many times in a loop, I am seeing a run queue corruption: > >> https://gist.github.com/jerrinsg/0ab09cd435d8d2cb6ae692c7e6f4f26b > >> > >> Is there anything wrong in the process dequeue or enqueue function that I have > >> written? Please help! > > > > volatile doesn't mean what you think it does, please don't use it in the > > kernel. > > > > This flag was to be used for synchronization. I will change this. > > > And why are you using "raw_spin_lock()"? > > I used this seeing other usage in sched/core.c. Can please you let me know if I > should instead use a different function to lock the run queue? Ah, don't know, don't mess with the scheduler, thankfully :) > >> Kernel used: Linux 3.13 > > > > Wow that's obsolete and buggy, why use such an old thing? > > This is the codebase that I inherited. Once I get the basic prototype working, I > will be working to port it to a newer version of the kernel. Try porting it to a modern kernel and then posting your real patch for review, that would make things a bit more obvious and probably show your bug better. good luck, greg k-h _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
