From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 1F5ED1FE46C for ; Mon, 2 Dec 2024 11:22:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733138528; cv=none; b=B+stOaeQY2cEc274BvO5vGPmvl9kPOpm4XrFRiCW2KrFdEn5mr3kEca094bx90P4DM81CxVkfFrB4TcdjEfYzrChXVb0QJ71W8+diRZeOGixUpo1pgRQ1Imzjp1rUMo/FwvzYySkhfK6fQTosqGmeGOYfmjIla5jnbXpkisQB/4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733138528; c=relaxed/simple; bh=aKC5m8Te3KxTEdZNz2E/rO1mlGWhjourLbO6QpI5uH0=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=XIsHdWU2rd59WOOzAAneq+qxlTBjoMU6zZ7B0/3o+CJDR9R5/ldXrXHd+TPymHgck6v4e1VPE3fzn7pRgWTEef4jwFfMZDlw0VpFSmkD49XDZBZUgAQoIwdQkRhcSuRKPDU10QApgropHtEgIVpHLIpkFPcg6FC833RqfHr6WjY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=c87NugaE; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="c87NugaE" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D4627C4CED1; Mon, 2 Dec 2024 11:22:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1733138527; bh=aKC5m8Te3KxTEdZNz2E/rO1mlGWhjourLbO6QpI5uH0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=c87NugaEjNKKTPM/z0lz9VdoOrDqtpqOTBEC8jUCWTMoK0S2qJsJP3NzuKbW5TJsC D1Glbqrc0nYR1ID+fmI1ciPx7PUfvYtOzPiTytdAE/fBqYv7Qr2VGTxfbzEWnsVChY HxrwOPGLYFP1wmPJx/JyYAFewQbBX63RfFltsEWNT8gNe4w7bqfsv8RiVi1iQwMgw+ CrLk7qGQTP+ujusSnnzVEL6tisVVYR/g7TzMsWGhPoNWNK2uqgWPlEpQJwdxhjHcUc b2ZLoQj5Y+aOG2kxU+t9jNZDHV42G2fSaswlIs7ImaMGxwKV+NB0l8PMwKA+ChL2Y/ RqTMYKQuWq54A== Date: Mon, 2 Dec 2024 11:22:02 +0000 From: Conor Dooley To: guoren@kernel.org Cc: paul.walmsley@sifive.com, palmer@dabbelt.com, bjorn@rivosinc.com, leobras@redhat.com, peterz@infradead.org, parri.andrea@gmail.com, will@kernel.org, longman@redhat.com, boqun.feng@gmail.com, arnd@arndb.de, alexghiti@rivosinc.com, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, Guo Ren Subject: Re: [RESEND PATCH] riscv: Fixup boot failure when CONFIG_DEBUG_RT_MUTEXES=y Message-ID: <20241202-vertigo-dreamboat-4bf6b61a4ef6@spud> References: <20241130153310.3349484-1-guoren@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="PNVedD9oKqNR10oc" Content-Disposition: inline In-Reply-To: <20241130153310.3349484-1-guoren@kernel.org> --PNVedD9oKqNR10oc Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Sat, Nov 30, 2024 at 10:33:10AM -0500, guoren@kernel.org wrote: > From: Guo Ren >=20 > When CONFIG_DEBUG_RT_MUTEXES=3Dy, mutex_lock->rt_mutex_try_acquire > would change from rt_mutex_cmpxchg_acquire to > rt_mutex_slowtrylock(): > raw_spin_lock_irqsave(&lock->wait_lock, flags); > ret =3D __rt_mutex_slowtrylock(lock); > raw_spin_unlock_irqrestore(&lock->wait_lock, flags); >=20 > Because queued_spin_#ops to ticket_#ops is changed one by one by > jump_label, raw_spin_lock/unlock would cause a deadlock during the > changing. >=20 > That means in arch/riscv/kernel/jump_label.c: > 1. > arch_jump_label_transform_queue() -> > mutex_lock(&text_mutex); +-> raw_spin_lock -> queued_spin_lock > |-> raw_spin_unlock -> queued_spin_unlock > patch_insn_write -> change the raw_spin_lock to ticket_lock > mutex_unlock(&text_mutex); > ... >=20 > 2. /* Dirty the lock value */ > arch_jump_label_transform_queue() -> > mutex_lock(&text_mutex); +-> raw_spin_lock -> *ticket_lock* > |-> raw_spin_unlock -> *queued_spin_unlock* > /* BUG: ticket_lock with queued_spin_unlock */ > patch_insn_write -> change the raw_spin_unlock to ticket_unlock > mutex_unlock(&text_mutex); > ... >=20 > 3. /* Dead lock */ > arch_jump_label_transform_queue() -> > mutex_lock(&text_mutex); +-> raw_spin_lock -> ticket_lock /* deadlock! */ > |-> raw_spin_unlock -> ticket_unlock > patch_insn_write -> change other raw_spin_#op -> ticket_#op > mutex_unlock(&text_mutex); >=20 > So, the solution is to disable mutex usage of > arch_jump_label_transform_queue() during early_boot_irqs_disabled, just > like we have done for stop_machine. >=20 > Reported-by: Conor Dooley Tested-by: Conor Dooley Thanks, Conor. --PNVedD9oKqNR10oc Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iHUEABYIAB0WIQRh246EGq/8RLhDjO14tDGHoIJi0gUCZ02YOAAKCRB4tDGHoIJi 0u4tAQD6SZZZiL32ZYOosf6OYXIcB58LwhhQx8q9rpkdOJ83MwEAz5fGQp47QqnL p4h17qAfQMMQncnXded5i6hV9r39kQo= =MpJM -----END PGP SIGNATURE----- --PNVedD9oKqNR10oc--