On 06/06/2017 05:01 PM, Larry Finger wrote: > On 06/06/2017 09:02 AM, Vlastimil Babka wrote: >> On 06/05/2017 11:44 PM, Andrew Morton wrote: >>> On Sat, 3 Jun 2017 14:24:26 -0500 Larry Finger <Larry.Finger@xxxxxxxxxxxx> wrote: >>> >>>> I recently turned on locking diagnostics for a Dell Latitude D600 laptop, which >>>> requires a 32-bit kernel. In the log I found the following: >>>> >>>> BUG: sleeping function called from invalid context at mm/khugepaged.c:655 >>>> in_atomic(): 1, irqs_disabled(): 0, pid: 20, name: khugepaged >>>> 1 lock held by khugepaged/20: >>>> #0: (&mm->mmap_sem){++++++}, at: [<c03d6609>] >>>> collapse_huge_page.isra.47+0x439/0x1240 >>>> CPU: 0 PID: 20 Comm: khugepaged Tainted: G W >> >> W means thre was WARN earler. Could be related... Got logs? > > When I grabbed a splat, I got the last one in my log. The first one shows "Not > tainted". > >> >>>> 4.12.0-rc1-wl-12125-g952a068 #80 >> >> What is "wl-12125-g952a068"? What patches on top of mainline? > > I found this while chasing a problem with one of the wireless drivers. For that > reason I use Kalle Valo's wireless-testing-next, which happens to be the only > kernel tree I have on this laptop. I'm reasonably certain that the extra updates > are not the cause of the problem as the first one appears before any of the > wireless drivers are loaded, but I will pull a clean copy of mainline to test > that assumption. > >>>> Hardware name: Dell Computer Corporation Latitude D600 >>>> /03U652, BIOS A05 05/29/2003 >>>> Call Trace: >>>> dump_stack+0x76/0xb2 >>>> ___might_sleep+0x174/0x230 >>>> collapse_huge_page.isra.47+0xacf/0x1240 >>>> khugepaged_scan_mm_slot+0x41e/0xc00 >>>> ? _raw_spin_lock+0x46/0x50 >>>> khugepaged+0x277/0x4f0 >>>> ? prepare_to_wait_event+0xe0/0xe0 >>>> kthread+0xeb/0x120 >>>> ? khugepaged_scan_mm_slot+0xc00/0xc00 >>>> ? kthread_create_on_node+0x30/0x30 >>>> ret_from_fork+0x21/0x30 >>>> >>>> I have no idea when this problem was introduced. Of course, I will test any >>>> proposed fixes. >>>> >>> >>> Odd. There's nothing wrong with cond_resched() while holding mmap_sem. >>> It looks like khugepaged forgot to do a spin_unlock somewhere and we >>> leaked a preempt_count. >> >> Hmm I'd expect such spin lock to be reported together with mmap_sem in >> the debugging "locks held" message? > > My bisection of the problem is about half done. My latest good version is commit > 7b8cd33 and the latest bad one is 2ea659a. Only about 7 steps to go. Hmm, your bisection will most likely just find commit 338a16ba15495 which added the cond_resched() at mm/khugepaged.c:655. CCing David who added it. -- 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>