Hi Peter, On Tue, Jan 19, 2016 at 1:13 AM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote: > On Mon, Jan 18, 2016 at 11:24:21PM +0800, gavin.guo@xxxxxxxxxxxxx wrote: >> From: Gavin Guo <gavin.guo@xxxxxxxxxxxxx> >> >> The following message can be observed on the Ubuntu v3.13.0-65 with KASan >> backported: > > <snip> > >> As commit 1effd9f19324 ("sched/numa: Fix unsafe get_task_struct() in >> task_numa_assign()") points out, the rcu_read_lock() cannot protect the >> task_struct from being freed in the finish_task_switch(). And the bug >> happens in the process of calculation of imp which requires the access of >> p->numa_faults being freed in the following path: >> >> do_exit() >> current->flags |= PF_EXITING; >> release_task() >> ~~delayed_put_task_struct()~~ >> schedule() >> ... >> ... >> rq->curr = next; >> context_switch() >> finish_task_switch() >> put_task_struct() >> __put_task_struct() >> task_numa_free() >> >> The fix here to get_task_struct() early before end of dst_rq->lock to >> protect the calculation process and also put_task_struct() in the >> corresponding point if finally the dst_rq->curr somehow cannot be >> assigned. >> >> v1->v2: >> - Fix coding style suggested by Peter Zijlstra. >> >> Signed-off-by: Gavin Guo <gavin.guo@xxxxxxxxxxxxx> >> Signed-off-by: Liang Chen <liangchen.linux@xxxxxxxxx> > > Argh, sorry for not noticing before; this SoB chain is not valid. > > Gavin wrote (per From) and send me the patch (per actual email headers), > so Liang never touched it. > > Should that be a reviewed-by for him? Liang is also the co-author of the original patch, we figured out the code by parallel programming, part of the idea was came from him. If SoB is not valid, can I change the line to the following? Co-authored-by: Liang Chen <liangchen.linux@xxxxxxxxx> -- 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>