linux-kernel - [PATCH] PCI/P2PDMA: Save a few cycles in 'pci_alloc

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Message-Id: <ab80164f4d5b32f9e6240aa4863c3a147ff9c89f.1635974126.git.christophe.jaillet@wanadoo.fr>
Date:   Wed,  3 Nov 2021 22:16:53 +0100
From:   Christophe JAILLET <christophe.jaillet@...adoo.fr>
To:     bhelgaas@...gle.com
Cc:     linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-janitors@...r.kernel.org,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>
Subject: [PATCH] PCI/P2PDMA: Save a few cycles in 'pci_alloc_p2pmem()'

Use 'percpu_ref_tryget_live_rcu()' instead of 'percpu_ref_tryget_live()' to
save a few cycles when it is known that the rcu lock is already
taken/released.

Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
---
 drivers/pci/p2pdma.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c
index 8d47cb7218d1..081c391690d4 100644
--- a/drivers/pci/p2pdma.c
+++ b/drivers/pci/p2pdma.c
@@ -710,7 +710,7 @@ void *pci_alloc_p2pmem(struct pci_dev *pdev, size_t size)
 	if (!ret)
 		goto out;
 
-	if (unlikely(!percpu_ref_tryget_live(ref))) {
+	if (unlikely(!percpu_ref_tryget_live_rcu(ref))) {
 		gen_pool_free(p2pdma->pool, (unsigned long) ret, size);
 		ret = NULL;
 		goto out;
-- 
2.30.2