* Mark Rutland <[email protected]> wrote:
> On Tue, Jul 24, 2018 at 11:20:36AM +0200, Peter Zijlstra wrote: > > On Tue, Jul 24, 2018 at 09:15:18AM +0200, Ingo Molnar wrote: > > > > > > * Mark Rutland <[email protected]> wrote: > > > > > > > From: Peter Zijlstra <[email protected]> > > > > > > > > Mark found ldsem_cmpxchg() needed an (atomic_long_t *) cast to keep > > > > working after making the atomic_long interface type safe. > > > > > > > > Needing casts is bad form, which made me look at the code. There are no > > > > ld_semaphore::count users outside of these functions so there is no > > > > reason why it can not be an atomic_long_t in the first place, obviating > > > > the need for this cast. > > > > > > > > That also ensures the loads use atomic_long_read(), which implies (at > > > > least) READ_ONCE() in order to guarantee single-copy-atomic loads. > > > > > > > > When using atomic_long_try_cmpxchg() the ldsem_cmpxchg() wrapper gets > > > > very thin (the only difference is not changing *old on success, which > > > > most callers don't seem to care about). > > > > > > > > So rework the whole thing to use atomic_long_t and its accessors > > > > directly. > > > > > > > > While there, fixup all the horrible comment styles. > > > > > > > > Cc: Peter Hurley <[email protected]> > > > > Acked-by: Will Deacon <[email protected]> > > > > Reported-by: Mark Rutland <[email protected]> > > > > Reviewed-by: Andy Shevchenko <[email protected]> > > > > Signed-off-by: Peter Zijlstra (Intel) <[email protected]> > > > > Signed-off-by: Mark Rutland <[email protected]> > > > > Cc: Ingo Molnar <[email protected]> > > > > --- > > > > drivers/tty/tty_ldsem.c | 82 > > > > ++++++++++++++++++++--------------------------- > > > > include/linux/tty_ldisc.h | 4 +-- > > > > 2 files changed, 37 insertions(+), 49 deletions(-) > > > > > > > > Note: Greg has queued this via the in the tty tree for v4.19, which can > > > > be seen at: > > > > > > > > https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty.git/commit/?h=tty-next&id=5fd691afdf929061c391d897fa627822c3b2fd5a > > > > > > Can this patch be skipped, or do the others depend on it? > > > > IIRC it depends on it, without this patch you get build issues due to > > atomic_long_cmpxchg() getting picky about it's arguments (type safety > > improved). > > Yup. Without this patch, there will be a build regression at patch 9, > when we move to generated atomic_long_*() wrappers. Ok, then these bits will have to wait until Greg's tree goes upstream in about two weeks. Which patches can I apply as a preparatory step? Thanks, Ingo
