On Wed, Jun 17, 2020 at 12:46:58PM +0206, John Ogness wrote: > The MNT_WRITE_HOLD flag is used to manually implement a per-cpu > optimized rwsem using busy waiting. This implementation is a problem > on PREEMPT_RT because write_seqlock() on @mount_lock (i.e. taking a > spinlock) does not disable preemption. This allows a writer to > preempt a task that has set MNT_WRITE_HOLD and thus that writer will > live lock in __mnt_want_write() due to busy looping with preemption > disabled. > Why can't you use a regular percpu-rwsem for this?
