Issue #2338 has been updated by Venkatesh Srinivas. Status changed from In Progress to Resolved
I think this bug has been resolved by commit 2a9bfc81fff48191a76fdf894657083e091df58a. ---------------------------------------- Bug #2338: vm_pageout_active_scan panic http://bugs.dragonflybsd.org/issues/2338 Author: Venkatesh Srinivas Status: Resolved Priority: Normal Assignee: Category: Target version: A panic was seen on x86-64 where vm_pageout_active_scan() had removed a page from the active queue and found the object pointer nulled. The offending code section is roughly at line 1245 of vm_pageout.c (vm_pageout_active_scan(); we have found & busied the page, unlocked the queues; testing refcount). (panic seen by sephe@) 1) vm_pageout_scan_active got an active page off of PQ_ACTIVE. The page was referenced, busy, PG_CLEANCHKed, and PG_NEED_COMMITed. The page's m->object field was NULL, but m->pindex was not, pointing to a recent vm_page_remove() {which does not erase pindex}. 2) At first glance, it looks like vm_pageout_scan_active() and vm_page_remove() might have a race; specifically: vm_pageout_scan_active ... * Lock page queue for page we selected * Try to busy page (PG_BUSY set) * If successful, unlock page queue for the page and the page spinlock too * yield() vm_page_remove() * hold the vm_object for the pg This should be safe, because the page was PG_BUSY. But perhaps one caller is not correctly busying the page? * spinlock the page * remove the page from the obj * spinunlock the page * drop the object * find m->object NULL ! Surprise! -- You have received this notification because you have either subscribed to it, or are involved in it. To change your notification preferences, please click here: http://bugs.dragonflybsd.org/my/account
