Messages in this thread Patch in this message | ![/](/images/icornerl.gif) | | From | Sebastian Andrzej Siewior <> | Subject | [PATCH net-next 05/24] net/tcp_sigpool: Use nested-BH locking for sigpool_scratch. | Date | Fri, 15 Dec 2023 18:07:24 +0100 |
| |
sigpool_scratch is a per-CPU variable and relies on disabled BH for its locking. Without per-CPU locking in local_bh_disable() on PREEMPT_RT this data structure requires explicit locking.
Make a struct with a pad member (original sigpool_scratch) and a local_lock_t and use local_lock_nested_bh() for locking. This change adds only lockdep coverage and does not alter the functional behaviour for !PREEMPT_RT.
Cc: David Ahern <dsahern@kernel.org> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> --- net/ipv4/tcp_sigpool.c | 17 +++++++++++++---- 1 file changed, 13 insertions(+), 4 deletions(-)
diff --git a/net/ipv4/tcp_sigpool.c b/net/ipv4/tcp_sigpool.c index 55b310a722c7d..0046d1a0dd796 100644 --- a/net/ipv4/tcp_sigpool.c +++ b/net/ipv4/tcp_sigpool.c @@ -10,7 +10,14 @@ #include <net/tcp.h> static size_t __scratch_size; -static DEFINE_PER_CPU(void __rcu *, sigpool_scratch); +struct sigpool_scratch { + local_lock_t bh_lock; + void __rcu *pad; +}; + +static DEFINE_PER_CPU(struct sigpool_scratch, sigpool_scratch) = { + .bh_lock = INIT_LOCAL_LOCK(bh_lock), +}; struct sigpool_entry { struct crypto_ahash *hash; @@ -72,7 +79,7 @@ static int sigpool_reserve_scratch(size_t size) break; } - old_scratch = rcu_replace_pointer(per_cpu(sigpool_scratch, cpu), + old_scratch = rcu_replace_pointer(per_cpu(sigpool_scratch.pad, cpu), scratch, lockdep_is_held(&cpool_mutex)); if (!cpu_online(cpu) || !old_scratch) { kfree(old_scratch); @@ -93,7 +100,7 @@ static void sigpool_scratch_free(void) int cpu; for_each_possible_cpu(cpu) - kfree(rcu_replace_pointer(per_cpu(sigpool_scratch, cpu), + kfree(rcu_replace_pointer(per_cpu(sigpool_scratch.pad, cpu), NULL, lockdep_is_held(&cpool_mutex))); __scratch_size = 0; } @@ -278,7 +285,8 @@ int tcp_sigpool_start(unsigned int id, struct tcp_sigpool *c) __cond_acquires(RC /* Pairs with tcp_sigpool_reserve_scratch(), scratch area is * valid (allocated) until tcp_sigpool_end(). */ - c->scratch = rcu_dereference_bh(*this_cpu_ptr(&sigpool_scratch)); + local_lock_nested_bh(&sigpool_scratch.bh_lock); + c->scratch = rcu_dereference_bh(*this_cpu_ptr(&sigpool_scratch.pad)); return 0; } EXPORT_SYMBOL_GPL(tcp_sigpool_start); @@ -287,6 +295,7 @@ void tcp_sigpool_end(struct tcp_sigpool *c) __releases(RCU_BH) { struct crypto_ahash *hash = crypto_ahash_reqtfm(c->req); + local_unlock_nested_bh(&sigpool_scratch.bh_lock); rcu_read_unlock_bh(); ahash_request_free(c->req); crypto_free_ahash(hash); -- 2.43.0
| ![\](/images/icornerr.gif) |