From nobody Sun May 24 21:40:16 2026 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (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 4B3C3385D78; Thu, 21 May 2026 06:56:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.142.43.55 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779346566; cv=none; b=OV+KHotrdghIL0ZYetZAQwGcV7Bi8Nf4SsJpmxfIFGjvQOYYFJduFnYjBNs+G/sEEwvWUc8ibag/bmnhqdEdHFZSk9tZ7ywFzVTHHWRoKcdfeYPZGhx7KA7J6yXKIGVwmbiCt4JuwQe73TAo9MOPS31rr7UmN6kvu96P0aEhQNI= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779346566; c=relaxed/simple; bh=DYp7kJ6y/G+GQSUqvEG5cS3d3XsBWuJ57f+jIRRbr/k=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:To:Cc; b=bzYrDU8KAhBcIkAmL4vHZ4dKen9O4z+CPnNsfzx270E5DUq+pjv8sCpARyCVOyH8Q4s/8meljc9VQrW5lL3MR2Rp8ddxIb01zsIw36JLhWm1iu3VCRMRMyf3MDt4wHG/tBmHy1PugWNrK8aZwg2dkzflIoToaU/jN1v3D+8ucyc= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de; spf=pass smtp.mailfrom=linutronix.de; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=Kl7wdhS6; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=s4Q5vU07; arc=none smtp.client-ip=193.142.43.55 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="Kl7wdhS6"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="s4Q5vU07" From: Kurt Kanzenbach DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1779346563; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=GZ6CpHA8DCv1EO0Bfml/WPMS5eybBvYChyGfRu9Jp9E=; b=Kl7wdhS6Cq4F9VhTaGtppzYoYmhLKd2smgm5qhVCuMAPZy2191H3ebbOy0VxP+62Bj+TWz RrGSMfaq6mRiL3HVJq32aVojNyEOxIayznOlzqBAx2pJUeOu2gRlndYUPBUhrcJ+0OJEaj ZaT9EBtPyXqO/7CHXY5K2/tMRFqwJpPMzIBo2C1XEeIECZ3fNRyssI8zx90+FKaOJyzGpq pgwdN1Njh6/6x0axKAY/1QbYqcOZUtLIZ/PXr4yIvck1OlB57CX1s1To2B9aI67XL0R1QH Xz7y9IOO3rE8wFEa3qLKlr+5BhUoriuqPXbQXCu5zdd+01c6Zp08xqDuGC3YSQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1779346563; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=GZ6CpHA8DCv1EO0Bfml/WPMS5eybBvYChyGfRu9Jp9E=; b=s4Q5vU07x+aYnyw1eNTsNh5NVMjVc+eZwObfcQEraQ0uzD4vUOaEwsUw2a+Tkb/NZK+eGY I4FI/dikVpAFCOCw== Date: Thu, 21 May 2026 08:55:47 +0200 Subject: [PATCH RFC net] ptp: vclock: Switch from RCU to SRCU Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20260521-vclock_rcu-v1-1-9c345c18bd72@linutronix.de> X-B4-Tracking: v=1; b=H4sIAHKsDmoC/6tWKk4tykwtVrJSqFYqSi3LLM7MzwNyDHUUlJIzE vPSU3UzU4B8JSMDIzMDUyND3bLknPzk7Pii5FLdVCPLZMtkQwPzZOMkJaCGgqLUtMwKsGHRSkF uzgp5qSVKsRCJ4tKkrNTkEpBRSrW1AEJ3mh53AAAA X-Change-ID: 20260521-vclock_rcu-e29c9c107c3b To: Richard Cochran , Yangbo Lu , Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni Cc: =?utf-8?q?=C3=8D=C3=B1igo_Huguet?= , Miroslav Lichvar , Blanco Alcaine Hector , "Christopher S. Hall" , Sebastian Andrzej Siewior , Florian Zeitz , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Kurt Kanzenbach X-Developer-Signature: v=1; a=openpgp-sha256; l=2592; i=kurt@linutronix.de; h=from:subject:message-id; bh=DYp7kJ6y/G+GQSUqvEG5cS3d3XsBWuJ57f+jIRRbr/k=; b=owEBbQKS/ZANAwAKAcGT0fKqRnOCAcsmYgBqDqyDVsRtgZXldID3s4y01VmpzWr8W7G3J2CaP eae6IfOwo2JAjMEAAEKAB0WIQS8ub+yyMN909/bWZLBk9HyqkZzggUCag6sgwAKCRDBk9HyqkZz gsNzD/9fXEOcpEJeQxmngXGoqtI/VkmC+k2rJfeWqiPfdFMOnE7Mg+2gmgsYMwAvkWjV578jFjl cc1MfxrXiGQt4UWCnDWVkkmdJPsX30JRbABbd1E8S2/aBnINt7dhRqjfarRgw5ISDbYT+1RL0z3 E4HdjpIw/qmC5Wl1p5En4Y6qcA5w7gV5Vdj0sFyGlN+G6tvV1k2iBcoamzdW+IkJA42sisCZewx 64Za2TvRhCk2B/5tx8CkFn0HNaOYAQKl/31yx0wtOWMkWrHKGpMvpPdQivupk7zszX65GLW+/Gi 4EJrHVJaSXb0Sh4GpCaNesDdvK/dkNdy0lRDJK66E4r8M93m4jthqIbyeLZErWrpMAnz79G4YxA 2lSMxWyEYVFMBWYnn5OIzDuA8u/6XJsDYEWOgiTVzajplPp6mp9sJLCo68mP4SW/pBr1BFUPBhw gTk9xpoQRNUkwuPWmvBjrqYH2xl6ZHyMGBabshFTlZUFWT319AB69NzU5qZSzm04cO2rlMUJ17m GrA4XC5vaB3jHGfa7mRxRF4IvmFuBkra5sKI7XmtxM4JCFFdV/HsUiAewxr4FKbUz1MBZC2/Ve/ Na2CGy6uLWLLbtDRV2GmdW/ltXQPiwPz+IfQf19MhAGbj7oeShmowu5gt00VftqikYopaqoNv57 AZbdA6GeKo3DW8Q== X-Developer-Key: i=kurt@linutronix.de; a=openpgp; fpr=BCB9BFB2C8C37DD3DFDB5992C193D1F2AA467382 The usage of PTP vClocks leads immediately to the following issues with ptp4l with LOCKDEP and DEBUG_ATOMIC_SLEEP enabled: "BUG: sleeping function called from invalid context". ptp_convert_timestamp() acquires a mutex_t within a RCU read section. This is illegal, because acquiring a mutex_t can result in voluntary scheduling request which is not allowed within a RCU read section. Replace the RCU usage with SRCU where sleeping is allowed. Reported-by: Florian Zeitz Closes: https://lore.kernel.org/all/00a8cce8-410e-4038-98af-49be6d93d7bd@sc= hettke.com/ Fixes: 67d93ffc0f3c ("ptp: vclock: use mutex to fix "sleep on atomic" bug") Signed-off-by: Kurt Kanzenbach --- RFC. Maybe there is a better solution than using SRCU? --- drivers/ptp/ptp_vclock.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) diff --git a/drivers/ptp/ptp_vclock.c b/drivers/ptp/ptp_vclock.c index 915a4f6defc9..84cb527f59cc 100644 --- a/drivers/ptp/ptp_vclock.c +++ b/drivers/ptp/ptp_vclock.c @@ -19,6 +19,8 @@ static DEFINE_SPINLOCK(vclock_hash_lock); =20 static DEFINE_READ_MOSTLY_HASHTABLE(vclock_hash, 8); =20 +DEFINE_STATIC_SRCU(vclock_srcu); + static void ptp_vclock_hash_add(struct ptp_vclock *vclock) { spin_lock(&vclock_hash_lock); @@ -37,7 +39,7 @@ static void ptp_vclock_hash_del(struct ptp_vclock *vclock) =20 spin_unlock(&vclock_hash_lock); =20 - synchronize_rcu(); + synchronize_srcu(&vclock_srcu); } =20 static int ptp_vclock_adjfine(struct ptp_clock_info *ptp, long scaled_ppm) @@ -276,14 +278,16 @@ ktime_t ptp_convert_timestamp(const ktime_t *hwtstamp= , int vclock_index) { unsigned int hash =3D vclock_index % HASH_SIZE(vclock_hash); struct ptp_vclock *vclock; - u64 ns; u64 vclock_ns =3D 0; + int srcu_idx; + u64 ns; =20 ns =3D ktime_to_ns(*hwtstamp); =20 - rcu_read_lock(); + srcu_idx =3D srcu_read_lock(&vclock_srcu); =20 - hlist_for_each_entry_rcu(vclock, &vclock_hash[hash], vclock_hash_node) { + hlist_for_each_entry_srcu(vclock, &vclock_hash[hash], vclock_hash_node, + srcu_read_lock_held(&vclock_srcu)) { if (vclock->clock->index !=3D vclock_index) continue; =20 @@ -294,7 +298,7 @@ ktime_t ptp_convert_timestamp(const ktime_t *hwtstamp, = int vclock_index) break; } =20 - rcu_read_unlock(); + srcu_read_unlock(&vclock_srcu, srcu_idx); =20 return ns_to_ktime(vclock_ns); } --- base-commit: 830d8771ae3c7bc90a62dde76a6556e612529fbc change-id: 20260521-vclock_rcu-e29c9c107c3b Best regards, -- =20 Kurt Kanzenbach