Messages in this thread Patch in this message | | | From | "Joel Fernandes (Google)" <> | Subject | [PATCH rcu/dev -fixes 3/4] rcu/tree: Avoid using xchg() in kfree_call_rcu_add_ptr_to_bulk() | Date | Mon, 20 Apr 2020 11:38:36 -0400 |
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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
There is no need to use xchg(), the access is serialized by krcp->lock. The xchg() function adds some atomic barriers which remain hidden in x86's disassembly but are visible on ARM for instance.
Replace xchg() with a load + store.
Acked-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> --- kernel/rcu/tree.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index cd61649e1b001..f6eb3aee0935e 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -3088,7 +3088,8 @@ kfree_call_rcu_add_ptr_to_bulk(struct kfree_rcu_cpu *krcp, /* Check if a new block is required. */ if (!krcp->bhead || krcp->bhead->nr_records == KFREE_BULK_MAX_ENTR) { - bnode = xchg(&krcp->bcached, NULL); + bnode = krcp->bcached; + krcp->bcached = NULL; if (!bnode) { WARN_ON_ONCE(sizeof(struct kfree_rcu_bulk_data) > PAGE_SIZE); -- 2.26.1.301.g55bc3eb7cb9-goog
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