Hi, On Thu, Dec 14, 2017 at 04:23:43PM +0100, Christoph Hellwig wrote: > From: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx> > > The epoll code currently uses the unlocked waitqueue helpers for managing The userfaultfd code > fault_wqh, but instead of holding the waitqueue lock for this waitqueue > around these calls, it the waitqueue lock of fault_pending_wq, which is > a different waitqueue instance. Given that the waitqueue is not exposed > to the rest of the kernel this actually works ok at the moment, but > prevents the epoll locking rules from being enforced using lockdep. ditto > Switch to the internally locked waitqueue helpers instead. This means > that the lock inside fault_wqh now nests inside the fault_pending_wqh > lock, but that's not a problem since it was entireyl unused before. spelling: entirely > Signed-off-by: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx> > [hch: slight changelog updates] > Signed-off-by: Christoph Hellwig <hch@xxxxxx> Reviewed-by: Mike Rapoport <rppt@xxxxxxxxxxxxxxxxxx> > --- > fs/userfaultfd.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c > index ac9a4e65ca49..a39bc3237b68 100644 > --- a/fs/userfaultfd.c > +++ b/fs/userfaultfd.c > @@ -879,7 +879,7 @@ static int userfaultfd_release(struct inode *inode, struct file *file) > */ > spin_lock(&ctx->fault_pending_wqh.lock); > __wake_up_locked_key(&ctx->fault_pending_wqh, TASK_NORMAL, &range); > - __wake_up_locked_key(&ctx->fault_wqh, TASK_NORMAL, &range); > + __wake_up(&ctx->fault_wqh, TASK_NORMAL, 1, &range); > spin_unlock(&ctx->fault_pending_wqh.lock); > > /* Flush pending events that may still wait on event_wqh */ > @@ -1045,7 +1045,7 @@ static ssize_t userfaultfd_ctx_read(struct userfaultfd_ctx *ctx, int no_wait, > * anyway. > */ > list_del(&uwq->wq.entry); > - __add_wait_queue(&ctx->fault_wqh, &uwq->wq); > + add_wait_queue(&ctx->fault_wqh, &uwq->wq); > > write_seqcount_end(&ctx->refile_seq); > > @@ -1194,7 +1194,7 @@ static void __wake_userfault(struct userfaultfd_ctx *ctx, > __wake_up_locked_key(&ctx->fault_pending_wqh, TASK_NORMAL, > range); > if (waitqueue_active(&ctx->fault_wqh)) > - __wake_up_locked_key(&ctx->fault_wqh, TASK_NORMAL, range); > + __wake_up(&ctx->fault_wqh, TASK_NORMAL, 1, range); > spin_unlock(&ctx->fault_pending_wqh.lock); > } > > -- > 2.14.2 > -- Sincerely yours, Mike.
