On Tue, Jul 05, 2022 at 08:00:42PM -0700, Andrew Morton wrote: > On Wed, 6 Jul 2022 10:47:32 +0800 Muchun Song <songmuc...@bytedance.com> > wrote: > > > > If this wakeup is not one of these, then are there reports from the > > > softlockup detector? > > > > > > Do we have reports of processes permanently stuck in D state? > > > > > > > No. The task is in an TASK_INTERRUPTIBLE state (see > > __fuse_dax_break_layouts). > > The hung task reporter only reports D task (TASK_UNINTERRUPTIBLE). > > Thanks, I updated the changelog a bit. > > : FSDAX page refcounts are 1-based, rather than 0-based: if refcount is > : 1, then the page is freed. The FSDAX pages can be pinned through GUP, > : then they will be unpinned via unpin_user_page() using a folio variant > : to put the page, however, folio variants did not consider this special > : case, the result will be to miss a wakeup event (like the user of > : __fuse_dax_break_layouts()). This results in a task being permanently > : stuck in TASK_INTERRUPTIBLE state. > : > : Since FSDAX pages are only possibly obtained by GUP users, so fix GUP > : instead of folio_put() to lower overhead. > > I believe these details are helpful for -stable maintainers who are > wondering why they were sent stuff. Also for maintainers of > downstreeam older kernels who are scratching heads over some user bug > report, trying to find a patch which might fix it - for this they want > to see a description of the user-visible effects, for matching with > that bug report. >
Thanks Andrew, it's really helpful.
