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Mon, 25 May 2026 12:49:47 -0700 (PDT) Received: from mozart.vkv.me ([2001:5a8:468b:d015:2feb:307b:ed4b:5f1d]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-30452230dddsm11032141eec.17.2026.05.25.12.49.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 25 May 2026 12:49:47 -0700 (PDT) From: Calvin Owens To: linux-kernel@vger.kernel.org Cc: Rodolfo Giometti , Sebastian Andrzej Siewior , Clark Williams , Steven Rostedt , Thomas Gleixner , Ingo Molnar , Greg Kroah-Hartman , Michael Byczkowski , Eliav Farber , linux-rt-devel@lists.linux.dev, David Laight Subject: [PATCH v6 2/3] pps: kc: convert pps_kc_hardpps_lock to raw_spinlock_t Date: Mon, 25 May 2026 12:49:31 -0700 Message-ID: X-Mailer: git-send-email 2.47.3 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Michael Byczkowski pps_kc_hardpps_lock is held in pps_kc_event(), which calls hardpps(). hardpps() takes tk_core.lock, which is already a raw_spinlock_t -- and nesting a sleeping lock (PREEMPT_RT's spinlock_t) over a raw_spinlock_t is invalid. Convert pps_kc_hardpps_lock and its call sites in kc.c to raw_spinlock_t to make the nesting valid on PREEMPT_RT. While here, refactor pps_kc_bind() and pps_kc_remove() to use guard(raw_spinlock_irq) for scope-based lock release. This eliminates four duplicated unlock call sites in pps_kc_bind() and the ambiguous bracket structure that resulted from them. Behavior is unchanged. No functional change on non-RT kernels. Tested-by: Michael Byczkowski Tested-by: Calvin Owens Acked-by: Rodolfo Giometti Signed-off-by: Michael Byczkowski Signed-off-by: Calvin Owens --- drivers/pps/kc.c | 67 ++++++++++++++++++++++-------------------------- 1 file changed, 31 insertions(+), 36 deletions(-) diff --git a/drivers/pps/kc.c b/drivers/pps/kc.c index fbd23295afd7..715b775e9679 100644 --- a/drivers/pps/kc.c +++ b/drivers/pps/kc.c @@ -21,7 +21,7 @@ */ /* state variables to bind kernel consumer */ -static DEFINE_SPINLOCK(pps_kc_hardpps_lock); +static DEFINE_RAW_SPINLOCK(pps_kc_hardpps_lock); /* PPS API (RFC 2783): current source and mode for kernel consumer */ static struct pps_device *pps_kc_hardpps_dev; /* unique pointer to device */ static int pps_kc_hardpps_mode; /* mode bits for kernel consumer */ @@ -36,35 +36,31 @@ static int pps_kc_hardpps_mode; /* mode bits for kernel consumer */ int pps_kc_bind(struct pps_device *pps, struct pps_bind_args *bind_args) { /* Check if another consumer is already bound */ - spin_lock_irq(&pps_kc_hardpps_lock); + guard(raw_spinlock_irq)(&pps_kc_hardpps_lock); - if (bind_args->edge == 0) - if (pps_kc_hardpps_dev == pps) { - pps_kc_hardpps_mode = 0; - pps_kc_hardpps_dev = NULL; - spin_unlock_irq(&pps_kc_hardpps_lock); - dev_info(&pps->dev, "unbound kernel" - " consumer\n"); - } else { - spin_unlock_irq(&pps_kc_hardpps_lock); - dev_err(&pps->dev, "selected kernel consumer" - " is not bound\n"); + if (bind_args->edge == 0) { + /* Unbind request */ + if (pps_kc_hardpps_dev != pps) { + dev_err(&pps->dev, + "selected kernel consumer is not bound\n"); return -EINVAL; } - else - if (pps_kc_hardpps_dev == NULL || - pps_kc_hardpps_dev == pps) { - pps_kc_hardpps_mode = bind_args->edge; - pps_kc_hardpps_dev = pps; - spin_unlock_irq(&pps_kc_hardpps_lock); - dev_info(&pps->dev, "bound kernel consumer: " - "edge=0x%x\n", bind_args->edge); - } else { - spin_unlock_irq(&pps_kc_hardpps_lock); - dev_err(&pps->dev, "another kernel consumer" - " is already bound\n"); + pps_kc_hardpps_mode = 0; + pps_kc_hardpps_dev = NULL; + dev_info(&pps->dev, "unbound kernel consumer\n"); + } else { + /* Bind request */ + if (pps_kc_hardpps_dev && pps_kc_hardpps_dev != pps) { + dev_err(&pps->dev, + "another kernel consumer is already bound\n"); return -EINVAL; } + pps_kc_hardpps_mode = bind_args->edge; + pps_kc_hardpps_dev = pps; + dev_info(&pps->dev, + "bound kernel consumer: edge=0x%x\n", + bind_args->edge); + } return 0; } @@ -78,15 +74,14 @@ int pps_kc_bind(struct pps_device *pps, struct pps_bind_args *bind_args) */ void pps_kc_remove(struct pps_device *pps) { - spin_lock_irq(&pps_kc_hardpps_lock); - if (pps == pps_kc_hardpps_dev) { - pps_kc_hardpps_mode = 0; - pps_kc_hardpps_dev = NULL; - spin_unlock_irq(&pps_kc_hardpps_lock); - dev_info(&pps->dev, "unbound kernel consumer" - " on device removal\n"); - } else - spin_unlock_irq(&pps_kc_hardpps_lock); + guard(raw_spinlock_irq)(&pps_kc_hardpps_lock); + + if (pps != pps_kc_hardpps_dev) + return; + + pps_kc_hardpps_mode = 0; + pps_kc_hardpps_dev = NULL; + dev_info(&pps->dev, "unbound kernel consumer on device removal\n"); } /* pps_kc_event - call hardpps() on PPS event @@ -102,8 +97,8 @@ void pps_kc_event(struct pps_device *pps, struct pps_event_time *ts, unsigned long flags; /* Pass some events to kernel consumer if activated */ - spin_lock_irqsave(&pps_kc_hardpps_lock, flags); + raw_spin_lock_irqsave(&pps_kc_hardpps_lock, flags); if (pps == pps_kc_hardpps_dev && event & pps_kc_hardpps_mode) hardpps(&ts->ts_real, &ts->ts_raw); - spin_unlock_irqrestore(&pps_kc_hardpps_lock, flags); + raw_spin_unlock_irqrestore(&pps_kc_hardpps_lock, flags); } -- 2.47.3