On Wed, 31 Jul 2019, Jan Kara wrote: > On Tue 30-07-19 13:24:54, Thomas Gleixner wrote: > > Bit spinlocks are problematic if PREEMPT_RT is enabled, because they > > disable preemption, which is undesired for latency reasons and breaks when > > regular spinlocks are taken within the bit_spinlock locked region because > > regular spinlocks are converted to 'sleeping spinlocks' on RT. So RT > > replaces the bit spinlocks with regular spinlocks to avoid this problem. > > > > To avoid ifdeffery at the source level, wrap all BH_Uptodate_Lock bitlock > > operations with inline functions, so the spinlock substitution can be done > > at one place. > > > > Using regular spinlocks can also be enabled for lock debugging purposes so > > the lock operations become visible to lockdep. > > > > Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> > > Cc: "Theodore Ts'o" <tytso@xxxxxxx> > > Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx> > > Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx> > > Cc: linux-fsdevel@xxxxxxxxxxxxxxx > > Looks good to me. You can add: > > Reviewed-by: Jan Kara <jack@xxxxxxx> > > BTW, it should be possible to get rid of BH_Uptodate_Lock altogether using > bio chaining (which was non-existent when this bh code was written) to make > sure IO completion function gets called only once all bios used to fill in > / write out the page are done. It would be also more efficient. But I guess > that's an interesting cleanup project for some other time... While 'possible cleanup' is something which triggers a certain nerve, that particular project certainly goes beyond my basic understanding of that whole fs/block conglomerate. I rather leave that to people who actually have a clue. :) Thanks, tglx
