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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Fri, 24 Nov 2023 10:11:03 +0100
Subject: [PATCH 05/15] net/tcp_sigpool: Use nested-BH locking for
sigpool_scratch.
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.10/older/patches-6.10.2-rt14.tar.xz
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(-)
--- 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_
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;
}
@@ -277,7 +284,8 @@ int tcp_sigpool_start(unsigned int id, s
/* 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);
@@ -286,6 +294,7 @@ void tcp_sigpool_end(struct tcp_sigpool
{
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);
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