On Mon, Mar 25, 2024 at 06:39:08PM +0100, Johannes Berg wrote: > From: Johannes Berg <[email protected]> > > When using "guard(rcu)();" sparse will complain, because even > though it now understands the cleanup attribute, it doesn't > evaluate the calls from it at function exit, and thus doesn't > count the context correctly. > > Given that there's a conditional in the resulting code: > > static inline void class_rcu_destructor(class_rcu_t *_T) > { > if (_T->lock) { > rcu_read_unlock(); > } > } > > it seems that even trying to teach sparse to evalulate the > cleanup attribute function it'd still be difficult to really > make it understand the full context here. > > Suppress the sparse warning by just releasing the context in > the acquisition part of the function, after all we know it's > safe with the guard, that's the whole point of it. > > Signed-off-by: Johannes Berg <[email protected]>
Reviewed-by: Boqun Feng <[email protected]> Regards, Boqun > --- > v2: add a comment after discussion with Boqun > > --- > include/linux/rcupdate.h | 14 +++++++++++++- > 1 file changed, 13 insertions(+), 1 deletion(-) > > diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h > index 0746b1b0b663..6a3c52b3c180 100644 > --- a/include/linux/rcupdate.h > +++ b/include/linux/rcupdate.h > @@ -1059,6 +1059,18 @@ rcu_head_after_call_rcu(struct rcu_head *rhp, > rcu_callback_t f) > extern int rcu_expedited; > extern int rcu_normal; > > -DEFINE_LOCK_GUARD_0(rcu, rcu_read_lock(), rcu_read_unlock()) > +DEFINE_LOCK_GUARD_0(rcu, > + do { > + rcu_read_lock(); > + /* > + * sparse doesn't call the cleanup function, > + * so just release immediately and don't track > + * the context. We don't need to anyway, since > + * the whole point of the guard is to not need > + * the explicit unlock. > + */ > + __release(RCU); > + } while(0), > + rcu_read_unlock()) > > #endif /* __LINUX_RCUPDATE_H */ > -- > 2.44.0 >
