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([140.116.96.205]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3030f7e9e3asm2272875a91.35.2025.03.21.10.20.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 21 Mar 2025 10:20:30 -0700 (PDT) From: Yu-Chun Lin To: isdn@linux-pingi.de, kuba@kernel.org Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, jserv@ccns.ncku.edu.tw, visitorckw@gmail.com, Yu-Chun Lin Subject: [PATCH] mISDN: hfcsusb: Optimize performance by replacing rw_lock with spinlock Date: Sat, 22 Mar 2025 01:20:24 +0800 Message-ID: <20250321172024.3372381-1-eleanor15x@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 The 'HFClock', an rwlock, is only used by writers, making it functionally equivalent to a spinlock. According to Documentation/locking/spinlocks.rst: "Reader-writer locks require more atomic memory operations than simple spinlocks. Unless the reader critical section is long, you are better off just using spinlocks." Since read_lock() is never called, switching to a spinlock reduces overhead and improves efficiency. Signed-off-by: Yu-Chun Lin --- Build tested only, as I don't have the hardware. Ensured all rw_lock -> spinlock conversions are complete, and replacing rw_lock with spinlock should always be safe. drivers/isdn/hardware/mISDN/hfcsusb.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/drivers/isdn/hardware/mISDN/hfcsusb.c b/drivers/isdn/hardware/mISDN/hfcsusb.c index e54419a4e731..5041d635ef7f 100644 --- a/drivers/isdn/hardware/mISDN/hfcsusb.c +++ b/drivers/isdn/hardware/mISDN/hfcsusb.c @@ -27,7 +27,7 @@ static unsigned int debug; static int poll = DEFAULT_TRANSP_BURST_SZ; static LIST_HEAD(HFClist); -static DEFINE_RWLOCK(HFClock); +static DEFINE_SPINLOCK(HFClock); MODULE_AUTHOR("Martin Bachem"); @@ -1895,9 +1895,9 @@ setup_instance(struct hfcsusb *hw, struct device *parent) goto out; hfcsusb_cnt++; - write_lock_irqsave(&HFClock, flags); + spin_lock_irqsave(&HFClock, flags); list_add_tail(&hw->list, &HFClist); - write_unlock_irqrestore(&HFClock, flags); + spin_unlock_irqrestore(&HFClock, flags); return 0; out: