From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6AD9D51B174; Wed, 30 Sep 2026 18:06:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790791572; cv=none; b=VpVxIQ5d4DkLY+nBHbq5dWbdL2bPRgOlaQYmWXpk5ByGw0iRWyqvGFsLC0KBpcIZEjT4+0b+WKjwrXDBKFoJsYmrmLlAeS3Hbu6E70RV6z1Vp/vZSvlkVhmHOUbEQGadM7KfQVl3Blbhk4eI9dRV/M/Hd+wWSI38wgSU7ze3Pdo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790791572; c=relaxed/simple; bh=BUGnrgDF602cYd129UrD0xfpd9dJq742YtWSjvvopL8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=XRPYWxkyFdurlrwi9qjMTJdffDbd4Y7IyMQh0kMPNrFxddIj2h9ACgLY3cr6bQcimtXJwo3ypNGrKhIFhkWNn8VpyJPJrNBvne9S4gJ/UdR0nEUZ6Dypjjn69pAJMipqoKma4AW4hQDsDhVSj9b3Rodb2SWOCt/OZ7Mat6opgok= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=EGCIcSxa; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="EGCIcSxa" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3D5871F000FF; Wed, 30 Sep 2026 18:06:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1790791570; bh=vpC2dqbhzNllEVbWV3eg0gWrIaqvPDY3EbOq6c6TtpI=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=EGCIcSxaILJShv2LhN+VVK00WTjMNHXy5iq8taSeQUFJ8kZpW/wHPlB7bilnsunrF ZoHJ/Pi2a2BhMOUqagioZ6pflaQwdGttYPKMGntIpc4v7KJCFz9iHFB49g0Hsa+wz4 K0vxIKzjZXydynOLAoJwVZfxOiQsRcWKmvbUF6F4= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Yannick Vignon , Jakub Kicinski , Sasha Levin Subject: [PATCH 5.15 348/752] net: stmmac: optimize locking around PTP clock reads Date: Wed, 30 Sep 2026 17:23:38 +0200 Message-ID: <20260930152405.819500131@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260930152358.131179731@linuxfoundation.org> References: <20260930152358.131179731@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Yannick Vignon [ Upstream commit 642436a1ad34a28c45bbc2bdc131640a73782356 ] Reading the PTP clock is a simple operation requiring only 3 register reads. Under a PREEMPT_RT kernel, protecting those reads by a spin_lock is counter-productive: if the 2nd task preempting the 1st has a higher prio but needs to read time as well, it will require 2 context switches, which will pretty much always be more costly than just disabling preemption for the duration of the reads. Moreover, with the code logic recently added to get_systime(), disabling preemption is not even required anymore: reads and writes just need to be protected from each other, to prevent a clock read while the clock is being updated. Improve the above situation by replacing the PTP spinlock by a rwlock, and using read_lock for PTP clock reads so simultaneous reads do not block each other. Signed-off-by: Yannick Vignon Link: https://lore.kernel.org/r/20220204135545.2770625-1-yannick.vignon@oss.nxp.com Signed-off-by: Jakub Kicinski Stable-dep-of: 0338c68e22ab ("net: stmmac: initialize ptp_lock at probe time") Signed-off-by: Sasha Levin --- .../net/ethernet/stmicro/stmmac/dwmac-intel.c | 4 ++-- drivers/net/ethernet/stmicro/stmmac/stmmac.h | 2 +- .../ethernet/stmicro/stmmac/stmmac_hwtstamp.c | 4 ++-- .../net/ethernet/stmicro/stmmac/stmmac_ptp.c | 22 +++++++++---------- .../stmicro/stmmac/stmmac_selftests.c | 8 +++---- 5 files changed, 20 insertions(+), 20 deletions(-) diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-intel.c b/drivers/net/ethernet/stmicro/stmmac/dwmac-intel.c index c9e88df9e8665..e6d01b10cf989 100644 --- a/drivers/net/ethernet/stmicro/stmmac/dwmac-intel.c +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-intel.c @@ -388,10 +388,10 @@ static int intel_crosststamp(ktime_t *device, /* Repeat until the timestamps are from the FIFO last segment */ for (i = 0; i < num_snapshot; i++) { - spin_lock_irqsave(&priv->ptp_lock, flags); + read_lock_irqsave(&priv->ptp_lock, flags); stmmac_get_ptptime(priv, ptpaddr, &ptp_time); *device = ns_to_ktime(ptp_time); - spin_unlock_irqrestore(&priv->ptp_lock, flags); + read_unlock_irqrestore(&priv->ptp_lock, flags); get_arttime(priv->mii, intel_priv->mdio_adhoc_addr, &art_time); *system = convert_art_to_tsc(art_time); } diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac.h b/drivers/net/ethernet/stmicro/stmmac/stmmac.h index 5946e1decd9cc..9ca1a69b3a9cb 100644 --- a/drivers/net/ethernet/stmicro/stmmac/stmmac.h +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac.h @@ -266,7 +266,7 @@ struct stmmac_priv { u32 adv_ts; int use_riwt; int irq_wake; - spinlock_t ptp_lock; + rwlock_t ptp_lock; /* Protects auxiliary snapshot registers from concurrent access. */ struct mutex aux_ts_lock; wait_queue_head_t tstamp_busy_wait; diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_hwtstamp.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_hwtstamp.c index 0d3d7874f0fc6..c0150c5d4781d 100644 --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_hwtstamp.c +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_hwtstamp.c @@ -206,9 +206,9 @@ static void timestamp_interrupt(struct stmmac_priv *priv) channel = ilog2(FIELD_GET(PTP_ACR_MASK, acr_value)); for (i = 0; i < num_snapshot; i++) { - spin_lock_irqsave(&priv->ptp_lock, flags); + read_lock_irqsave(&priv->ptp_lock, flags); get_ptptime(priv->ptpaddr, &ptp_time); - spin_unlock_irqrestore(&priv->ptp_lock, flags); + read_unlock_irqrestore(&priv->ptp_lock, flags); event.type = PTP_CLOCK_EXTTS; event.index = channel; event.timestamp = ptp_time; diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_ptp.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_ptp.c index e6221c33572d4..0ab5fca50b7bb 100644 --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_ptp.c +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_ptp.c @@ -39,9 +39,9 @@ static int stmmac_adjust_freq(struct ptp_clock_info *ptp, s32 ppb) diff = div_u64(adj, 1000000000ULL); addend = neg_adj ? (addend - diff) : (addend + diff); - spin_lock_irqsave(&priv->ptp_lock, flags); + write_lock_irqsave(&priv->ptp_lock, flags); stmmac_config_addend(priv, priv->ptpaddr, addend); - spin_unlock_irqrestore(&priv->ptp_lock, flags); + write_unlock_irqrestore(&priv->ptp_lock, flags); return 0; } @@ -86,9 +86,9 @@ static int stmmac_adjust_time(struct ptp_clock_info *ptp, s64 delta) mutex_unlock(&priv->plat->est->lock); } - spin_lock_irqsave(&priv->ptp_lock, flags); + write_lock_irqsave(&priv->ptp_lock, flags); stmmac_adjust_systime(priv, priv->ptpaddr, sec, nsec, neg_adj, xmac); - spin_unlock_irqrestore(&priv->ptp_lock, flags); + write_unlock_irqrestore(&priv->ptp_lock, flags); /* Caculate new basetime and re-configured EST after PTP time adjust. */ if (est_rst) { @@ -137,9 +137,9 @@ static int stmmac_get_time(struct ptp_clock_info *ptp, struct timespec64 *ts) unsigned long flags; u64 ns = 0; - spin_lock_irqsave(&priv->ptp_lock, flags); + read_lock_irqsave(&priv->ptp_lock, flags); stmmac_get_systime(priv, priv->ptpaddr, &ns); - spin_unlock_irqrestore(&priv->ptp_lock, flags); + read_unlock_irqrestore(&priv->ptp_lock, flags); *ts = ns_to_timespec64(ns); @@ -162,9 +162,9 @@ static int stmmac_set_time(struct ptp_clock_info *ptp, container_of(ptp, struct stmmac_priv, ptp_clock_ops); unsigned long flags; - spin_lock_irqsave(&priv->ptp_lock, flags); + write_lock_irqsave(&priv->ptp_lock, flags); stmmac_init_systime(priv, priv->ptpaddr, ts->tv_sec, ts->tv_nsec); - spin_unlock_irqrestore(&priv->ptp_lock, flags); + write_unlock_irqrestore(&priv->ptp_lock, flags); return 0; } @@ -193,12 +193,12 @@ static int stmmac_enable(struct ptp_clock_info *ptp, cfg->period.tv_sec = rq->perout.period.sec; cfg->period.tv_nsec = rq->perout.period.nsec; - spin_lock_irqsave(&priv->ptp_lock, flags); + write_lock_irqsave(&priv->ptp_lock, flags); ret = stmmac_flex_pps_config(priv, priv->ioaddr, rq->perout.index, cfg, on, priv->sub_second_inc, priv->systime_flags); - spin_unlock_irqrestore(&priv->ptp_lock, flags); + write_unlock_irqrestore(&priv->ptp_lock, flags); break; case PTP_CLK_REQ_EXTTS: priv->plat->ext_snapshot_en = on; @@ -302,7 +302,7 @@ void stmmac_ptp_register(struct stmmac_priv *priv) stmmac_ptp_clock_ops.n_per_out = priv->dma_cap.pps_out_num; stmmac_ptp_clock_ops.n_ext_ts = priv->dma_cap.aux_snapshot_n; - spin_lock_init(&priv->ptp_lock); + rwlock_init(&priv->ptp_lock); mutex_init(&priv->aux_ts_lock); priv->ptp_clock_ops = stmmac_ptp_clock_ops; diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_selftests.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_selftests.c index 4190d6c0d9e8e..f0259404077af 100644 --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_selftests.c +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_selftests.c @@ -1803,9 +1803,9 @@ static int stmmac_test_tbs(struct stmmac_priv *priv) if (ret) return ret; - spin_lock_irqsave(&priv->ptp_lock, flags); + read_lock_irqsave(&priv->ptp_lock, flags); stmmac_get_systime(priv, priv->ptpaddr, &curr_time); - spin_unlock_irqrestore(&priv->ptp_lock, flags); + read_unlock_irqrestore(&priv->ptp_lock, flags); if (!curr_time) { ret = -EOPNOTSUPP; @@ -1825,9 +1825,9 @@ static int stmmac_test_tbs(struct stmmac_priv *priv) goto fail_disable; /* Check if expected time has elapsed */ - spin_lock_irqsave(&priv->ptp_lock, flags); + read_lock_irqsave(&priv->ptp_lock, flags); stmmac_get_systime(priv, priv->ptpaddr, &curr_time); - spin_unlock_irqrestore(&priv->ptp_lock, flags); + read_unlock_irqrestore(&priv->ptp_lock, flags); if ((curr_time - start_time) < STMMAC_TBS_LT_OFFSET) ret = -EINVAL; -- 2.53.0