On Mon, May 8, 2023, at 04:01, Rohan McLure wrote: > Prior to this patch, data races are detectable by KCSAN of the following > forms: > > [1] Asynchronous calls to mmiowb_set_pending() from an interrupt context > or otherwise outside of a critical section > [2] Interrupted critical sections, where the interrupt will itself > acquire a lock > > In case [1], calling context does not need an mmiowb() call to be > issued, otherwise it would do so itself. Such calls to > mmiowb_set_pending() are either idempotent or no-ops. > > In case [2], irrespective of when the interrupt occurs, the interrupt > will acquire and release its locks prior to its return, nesting_count > will continue balanced. In the worst case, the interrupted critical > section during a mmiowb_spin_unlock() call observes an mmiowb to be > pending and afterward is interrupted, leading to an extraneous call to > mmiowb(). This data race is clearly innocuous. > > Mark all potentially asynchronous memory accesses with READ_ONCE or > WRITE_ONCE, including increments and decrements to nesting_count. This > has the effect of removing KCSAN warnings at consumer's callsites. > > Signed-off-by: Rohan McLure <rmcl...@linux.ibm.com> > Reported-by: Michael Ellerman <m...@ellerman.id.au> > Reported-by: Gautam Menghani <gautammenghani...@gmail.com> > --- > include/asm-generic/mmiowb.h | 17 +++++++++++------ > 1 file changed, 11 insertions(+), 6 deletions(-)
For asm-generic: Acked-by: Arnd Bergmann <a...@arndb.de>
