On Thu, Dec 19, 2024 at 02:42:00AM +0100, Antonio Quartulli wrote:
Similarly so kref_put_lock(), decrease the refcount and call bh_lock_sock(sk) if it reached 0.
This kref_put variant comes handy when in need of atomically cleanup any socket context along with setting the refcount to 0.
Cc: Will Deacon will@kernel.org (maintainer:ATOMIC INFRASTRUCTURE) Cc: Peter Zijlstra peterz@infradead.org (maintainer:ATOMIC INFRASTRUCTURE) Cc: Boqun Feng boqun.feng@gmail.com (reviewer:ATOMIC INFRASTRUCTURE) Cc: Mark Rutland mark.rutland@arm.com (reviewer:ATOMIC INFRASTRUCTURE) Cc: Andrew Morton akpm@linux-foundation.org Signed-off-by: Antonio Quartulli antonio@openvpn.net
include/linux/kref.h | 11 +++++++++++ include/linux/refcount.h | 3 +++ lib/refcount.c | 32 ++++++++++++++++++++++++++++++++
[...]
diff --git a/lib/refcount.c b/lib/refcount.c index a207a8f22b3ca35890671e51c480266d89e4d8d6..76a728581aa49a41ef13f5141f3f2e9816d72e75 100644 --- a/lib/refcount.c +++ b/lib/refcount.c @@ -7,6 +7,7 @@ #include <linux/refcount.h> #include <linux/spinlock.h> #include <linux/bug.h> +#include <net/sock.h> #define REFCOUNT_WARN(str) WARN_ONCE(1, "refcount_t: " str ".\n") @@ -156,6 +157,37 @@ bool refcount_dec_and_lock(refcount_t *r, spinlock_t *lock) } EXPORT_SYMBOL(refcount_dec_and_lock); +/**
- refcount_dec_and_lock_sock - return holding locked sock if able to decrement
refcount to 0
- @r: the refcount
- @sock: the sock to be locked
- Similar to atomic_dec_and_lock(), it will WARN on underflow and fail to
- decrement when saturated at REFCOUNT_SATURATED.
- Provides release memory ordering, such that prior loads and stores are done
- before, and provides a control dependency such that free() must come after.
- See the comment on top.
- Return: true and hold sock if able to decrement refcount to 0, false
otherwise- */
+bool refcount_dec_and_lock_sock(refcount_t *r, struct sock *sock) +{
- if (refcount_dec_not_one(r))
return false;- bh_lock_sock(sock);
- if (!refcount_dec_and_test(r)) {
bh_unlock_sock(sock);return false;- }
- return true;
+} +EXPORT_SYMBOL(refcount_dec_and_lock_sock);
It feels a little out-of-place to me having socket-specific functions in lib/refcount.c. I'd suggest sticking this somewhere else _or_ maybe we could generate this pattern of code:
#define REFCOUNT_DEC_AND_LOCKNAME(lockname, locktype, lock, unlock) \ static __always_inline \ bool refcount_dec_and_lock_##lockname(refcount_t *r, locktype *l) \ { \ ...
inside a generator macro in refcount.h, like we do for seqlocks in linux/seqlock.h. The downside of that is the cost of inlining.
Will