Messages in this thread | | | Date | Fri, 1 Jul 2022 14:49:57 +0200 | Subject | Re: [PATCH v7 2/4] kernfs: Change kernfs_notify_list to llist. | From | Marek Szyprowski <> |
| |
Hi,
On 01.07.2022 14:20, Imran Khan wrote: > On 1/7/22 9:22 pm, Marek Szyprowski wrote: >> On 15.06.2022 04:10, Imran Khan wrote: >>> At present kernfs_notify_list is implemented as a singly linked >>> list of kernfs_node(s), where last element points to itself and >>> value of ->attr.next tells if node is present on the list or not. >>> Both addition and deletion to list happen under kernfs_notify_lock. >>> >>> Change kernfs_notify_list to llist so that addition to list can heppen >>> locklessly. >>> >>> Suggested by: Al Viro <viro@zeniv.linux.org.uk> >>> Signed-off-by: Imran Khan <imran.f.khan@oracle.com> >>> Acked-by: Tejun Heo <tj@kernel.org> >> This patch landed in linux next-20220630 as commit b8f35fa1188b >> ("kernfs: Change kernfs_notify_list to llist."). Unfortunately, it >> causes serious regression on my test systems. It can be easily noticed >> in the logs by the following warning: >> >> ------------[ cut here ]------------ >> WARNING: CPU: 1 PID: 34 at fs/kernfs/dir.c:531 kernfs_put.part.0+0x1a4/0x1d8 >> kernfs_put: console/active: released with incorrect active_ref 0 >> Modules linked in: >> CPU: 1 PID: 34 Comm: kworker/1:4 Not tainted >> 5.19.0-rc4-05465-g5732b42edfd1 #12317 >> Hardware name: Samsung Exynos (Flattened Device Tree) >> Workqueue: events kernfs_notify_workfn >> unwind_backtrace from show_stack+0x10/0x14 >> show_stack from dump_stack_lvl+0x40/0x4c >> dump_stack_lvl from __warn+0xc8/0x13c >> __warn from warn_slowpath_fmt+0x90/0xb4 >> warn_slowpath_fmt from kernfs_put.part.0+0x1a4/0x1d8 >> kernfs_put.part.0 from kernfs_notify_workfn+0x1a0/0x1d0 >> kernfs_notify_workfn from process_one_work+0x1ec/0x4cc >> process_one_work from worker_thread+0x58/0x54c >> worker_thread from kthread+0xd0/0xec >> kthread from ret_from_fork+0x14/0x2c >> Exception stack(0xf099dfb0 to 0xf099dff8) >> ... >> ---[ end trace 0000000000000000 ]--- >> > Thanks for reporting this issue. It has been reported earlier in [1] as well. I > am unable to reproduce it locally. Could you please test with following patch on > top of linux next-20220630 and let me know if it helps:
Yes, this fixes the issue. Feel free to add:
Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Maybe it is related to the fact, that I have earlycon enabled on those machines?
> >From 6bf7f1adc4b091dc6d6c60e0dd0f16247f61f374 Mon Sep 17 00:00:00 2001 > From: Imran Khan <imran.f.khan@oracle.com> > Date: Fri, 1 Jul 2022 14:27:52 +1000 > Subject: [PATCH] kernfs: Avoid re-adding kernfs_node into kernfs_notify_list. > > --- > fs/kernfs/file.c | 9 ++++++--- > 1 file changed, 6 insertions(+), 3 deletions(-) > > diff --git a/fs/kernfs/file.c b/fs/kernfs/file.c > index bb933221b4bae..e8ec054e11c63 100644 > --- a/fs/kernfs/file.c > +++ b/fs/kernfs/file.c > @@ -917,6 +917,7 @@ static void kernfs_notify_workfn(struct work_struct *work) > if (free == NULL) > return; > > + free->next = NULL; > attr = llist_entry(free, struct kernfs_elem_attr, notify_next); > kn = attribute_to_node(attr, struct kernfs_node, attr); > root = kernfs_root(kn); > @@ -992,9 +993,11 @@ void kernfs_notify(struct kernfs_node *kn) > rcu_read_unlock(); > > /* schedule work to kick fsnotify */ > - kernfs_get(kn); > - llist_add(&kn->attr.notify_next, &kernfs_notify_list); > - schedule_work(&kernfs_notify_work); > + if (kn->attr.notify_next.next != NULL) { > + kernfs_get(kn); > + llist_add(&kn->attr.notify_next, &kernfs_notify_list); > + schedule_work(&kernfs_notify_work); > + } > } > EXPORT_SYMBOL_GPL(kernfs_notify); > > > base-commit: 6cc11d2a1759275b856e464265823d94aabd5eaf
Best regards -- Marek Szyprowski, PhD Samsung R&D Institute Poland
| |