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[177.4.161.87]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-2ee3889d634sm3714594eec.3.2026.04.30.20.28.44 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 30 Apr 2026 20:28:47 -0700 (PDT) Message-ID: <662ed68f-dd37-4a3e-821b-e2f715cb4a47@gmail.com> Date: Fri, 1 May 2026 00:28:40 -0300 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 1/2] firmware_loader: Add cancel helper for async requests To: Danilo Krummrich Cc: Luis Chamberlain , Russ Weight , Greg Kroah-Hartman , "Rafael J. Wysocki" , Takashi Iwai , Shenghao Ding , Kevin Lu , Baojun Xu , Jaroslav Kysela , driver-core@lists.linux.dev, linux-kernel@vger.kernel.org, linux-sound@vger.kernel.org, Takashi Iwai References: <20260430-alsa-hda-tas2781-fw-callback-teardown-v2-0-2c7d89cb3175@gmail.com> <20260430-alsa-hda-tas2781-fw-callback-teardown-v2-1-2c7d89cb3175@gmail.com> From: =?UTF-8?Q?C=C3=A1ssio_Gabriel_Monteiro_Pires?= Content-Language: en-US In-Reply-To: Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="------------YGdOVAJBVEA1TPH3T13ph9kG" This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --------------YGdOVAJBVEA1TPH3T13ph9kG Content-Type: multipart/mixed; boundary="------------aV2TDdxkkyQRlrI9J4ccR6AJ"; protected-headers="v1" From: =?UTF-8?Q?C=C3=A1ssio_Gabriel_Monteiro_Pires?= To: Danilo Krummrich Cc: Luis Chamberlain , Russ Weight , Greg Kroah-Hartman , "Rafael J. Wysocki" , Takashi Iwai , Shenghao Ding , Kevin Lu , Baojun Xu , Jaroslav Kysela , driver-core@lists.linux.dev, linux-kernel@vger.kernel.org, linux-sound@vger.kernel.org, Takashi Iwai Message-ID: <662ed68f-dd37-4a3e-821b-e2f715cb4a47@gmail.com> Subject: Re: [PATCH v2 1/2] firmware_loader: Add cancel helper for async requests References: <20260430-alsa-hda-tas2781-fw-callback-teardown-v2-0-2c7d89cb3175@gmail.com> <20260430-alsa-hda-tas2781-fw-callback-teardown-v2-1-2c7d89cb3175@gmail.com> In-Reply-To: Autocrypt-Gossip: addr=perex@perex.cz; keydata= xsFNBFvNeCsBEACUu2ZgwoGXmVFGukNPWjA68/7eMWI7AvNHpekSGv3z42Iy4DGZabs2Jtvk ZeWulJmMOh9ktP9rVWYKL9H54gH5LSdxjYYTQpSCPzM37nisJaksC8XCwD4yTDR+VFCtB5z/ E7U0qujGhU5jDTne3dZpVv1QnYHlVHk4noKxLjvEQIdJWzsF6e2EMp4SLG/OXhdC9ZeNt5IU HQpcKgyIOUdq+44B4VCzAMniaNLKNAZkTQ6Hc0sz0jXdq+8ZpaoPEgLlt7IlztT/MUcH3ABD LwcFvCsuPLLmiczk6/38iIjqMtrN7/gP8nvZuvCValLyzlArtbHFH8v7qO8o/5KXX62acCZ4 aHXaUHk7ahr15VbOsaqUIFfNxpthxYFuWDu9u0lhvEef5tDWb/FX+TOa8iSLjNoe69vMCj1F srZ9x2gjbqS2NgGfpQPwwoBxG0YRf6ierZK3I6A15N0RY5/KSFCQvJOX0aW8TztisbmJvX54 GNGzWurrztj690XLp/clewmfIUS3CYFqKLErT4761BpiK5XWUB4oxYVwc+L8btk1GOCOBVsp 4xAVD2m7M+9YKitNiYM4RtFiXwqfLk1uUTEvsaFkC1vu3C9aVDn3KQrZ9M8MBh/f2c8VcKbN njxs6x6tOdF5IhUc2E+janDLPZIfWDjYJ6syHadicPiATruKvwARAQABzSBKYXJvc2xhdiBL eXNlbGEgPHBlcmV4QHBlcmV4LmN6PsLBjgQTAQgAOBYhBF7f7LZepM3UTvmsRTCsxHw/elMJ BQJbzXgrAhsDBQsJCAcCBhUKCQgLAgQWAgMBAh4BAheAAAoJEDCsxHw/elMJDGAP/ReIRiRw lSzijpsGF/AslLEljncG5tvb/xHwCxK5JawIpViwwyJss06/IAvdY5vn5AdfUfCl2J+OakaR VM/hdHjCYNu4bdBYZQBmEiKsPccZG2YFDRudEmiaoaJ1e8ZsiA3rSf4SiWWsbcBOYHr/unTf 4KQsdUHzPUt8Ffi9HrAFzI2wjjiyV5yUGp3x58ZypAIMcKFtA1aDwhA6YmQ6lb8/bC0LTC6l cAAS1tj7YF5nFfXsodCOKK5rKf5/QOF0OCD2Gy+mGLNQnq6S+kD+ujQfOLaUHeyfcNBEBxda nZID7gzd65bHUMAeWttZr3m5ESrlt2SaNBddbN7NVpVa/292cuwDCLw2j+fAZbiVOYyqMSY4 LaNqmfa0wJAv30BMKeRAovozJy62j0AnntqrvtDqqvuXgYirj2BEDxx0OhZVqlI8o5qB6rA5 Pfp2xKRE8Fw3mASYRDNad08JDhJgsR/N5JDGbh4+6sznOA5J63TJ+vCFGM37M5WXInrZJBM3 ABicmpClXn42zX3Gdf/GMM3SQBrIriBtB9iEHQcRG/F+kkGOY4QDi4BZxo45KraANGmCkDk0 +xLZVfWh8YOBep+x2Sf83up5IMmIZAtYnxr77VlMYHDWjnpFnfuja+fcnkuzvvy7AHJZUO1A aKexwcBjfTxtlX4BiNoK+MgrjYywzsFNBFvNeCsBEACb8FXFMOw1g+IGVicWVB+9AvOLOhqI FMhUuDWmlsnT8B/aLxcRVUTXoNgJpt0y0SpWD3eEJOkqjHuvHfk+VhKWDsg6vlNUmF1Ttvob 18rce0UH1s+wlE8YX8zFgODbtRx8h/BpykwnuWNTiotu9itlE83yOUbv/kHOPUz4Ul1+LoCf V2xXssYSEnNr+uUG6/xPnaTvKj+pC7YCl38Jd5PgxsP3omW2Pi9T3rDO6cztu6VvR9/vlQ8Z t0p+eeiGqQV3I+7k+S0J6TxMEHI8xmfYFcaVDlKeA5asxkqu5PDZm3Dzgb0XmFbVeakI0be8 +mS6s0Y4ATtn/D84PQo4bvYqTsqAAJkApEbHEIHPwRyaXjI7fq5BTXfUO+++UXlBCkiH8Sle 2a8IGI1aBzuL7G9suORQUlBCxy+0H7ugr2uku1e0S/3LhdfAQRUAQm+K7NfSljtGuL8RjXWQ f3B6Vs7vo+17jOU7tzviahgeRTcYBss3e264RkL62zdZyyArbVbK7uIU6utvv0eYqG9cni+o z7CAe7vMbb5KfNOAJ16+znlOFTieKGyFQBtByHkhh86BQNQn77aESJRQdXvo5YCGX3BuRUaQ zydmrgwauQTSnIhgLZPv5pphuKOmkzvlCDX+tmaCrNdNc+0geSAXNe4CqYQlSnJv6odbrQlD Qotm9QARAQABwsF2BBgBCAAgFiEEXt/stl6kzdRO+axFMKzEfD96UwkFAlvNeCsCGwwACgkQ MKzEfD96Uwlkjg/+MZVS4M/vBbIkH3byGId/MWPy13QdDzBvV0WBqfnr6n99lf7tKKp85bpB y7KRAPtXu+9WBzbbIe42sxmWJtDFIeT0HJxPn64l9a1btPnaILblE1mrfZYAxIOMk3UZA3PH uFdyhQDJbDGi3LklDhsJFTAhBZI5xMSnqhaMmWCL99OWwfyJn2omp8R+lBfAJZR31vW6wzsj ssOvKIbgBpV/o3oGyAofIXPYzhY+jhWgOYtiPw9bknu748K+kK3fk0OeEG6doO4leB7LuWig dmLZkcLlJzSE6UhEwHZ8WREOMIGJnMF51WcF0A3JUeKpYYEvSJNDEm7dRtpb0x/Y5HIfrg5/ qAKutAYPY7ClQLu5RHv5uqshiwyfGPaiE8Coyphvd5YbOlMm3mC/DbEstHG7zA89fN9gAzsJ 0TFL5lNz1s/fo+//ktlG9H28EHD8WOwkpibsngpvY+FKUGfJgIxpmdXVOkiORWQpndWyRIqw k8vz1gDNeG7HOIh46GnKIrQiUXVzAuUvM5vI9YaW3YRNTcn3pguQRt+Tl9Y6G+j+yvuLL173 m4zRUU6DOygmpQAVYSOJvKAJ07AhQGaWAAi5msM6BcTU4YGcpW7FHr6+xaFDlRHzf1lkvavX WoxP1IA1DFuBMeYMzfyi4qDWjXc+C51ZaQd39EulYMh+JVaWRoY= --------------aV2TDdxkkyQRlrI9J4ccR6AJ Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Hi! On 4/30/26 19:44, Danilo Krummrich wrote: > On Thu Apr 30, 2026 at 11:15 PM CEST, C=C3=A1ssio Gabriel wrote: >> request_firmware_nowait() keeps the callback module pinned and holds >> a device reference until the firmware work completes. >> >> Callers still have no way to cancel or synchronize the queued callback= >> before tearing down their driver-private state. >> >> Track async firmware work with devres and add >> request_firmware_nowait_cancel(). >=20 > I assume this is needed for manual ordering in case the callback access= es > resources that are not managed by devres, but are released in remove().= >=20 > So, I think this is mixing two patterns, managed by the caller and devr= es > managed. >=20 > For the former we just want the ability to cancel things, this should b= e > compatible with the existing request_firmware_nowait(). >=20 > Note that some (hopefully most) drivers already open code synchronizati= on > patterns, e.g. a completion that is waited for in remove(). >=20 > However, some drivers also seem to just check a pointer, which is obvio= usly > vulnerable to TOCTOU races. >=20 > For a devres managed version, I think it should be a new API, > devm_request_firmware_nowait(), which should be possible to simply laye= r on top > of the existing API with devm_add_action(), so you can just call cancel= () from > the release callback. >=20 >> The helper cancels work that has not >> started yet and waits for an already-running callback to return. If th= e >> request has already completed, it is a no-op. >> >> The devres release path uses the same synchronization so device teardo= wn >> cannot free the firmware work state while the queued work can still ru= n. >> >> Signed-off-by: C=C3=A1ssio Gabriel >=20 > >=20 >> @@ -1184,18 +1213,19 @@ static int _request_firmware_nowait( >> =20 >> if (!uevent && fw_cache_is_setup(device, name)) { >> kfree_const(fw_work->name); >> - kfree(fw_work); >> + devres_free(fw_work); >> return -EOPNOTSUPP; >> } >> =20 >> if (!try_module_get(module)) { >> kfree_const(fw_work->name); >> - kfree(fw_work); >> + devres_free(fw_work); >> return -EFAULT; >> } >> =20 >> get_device(fw_work->device); >> INIT_WORK(&fw_work->work, request_firmware_work_func); >> + devres_add(device, fw_work); >=20 > This puts the requirement on request_firmware_nowait() that it must be = called > from a context where the device is guaranteed to not be unbound concurr= ently, > otherwise this may race with firmware_work_release(), which could free = fw_work > before this functions attempts to schedule it below. >=20 > As mentioned above, I think this patch should just add a cancel() funct= ion, so > we can layer devres managed functionality on top of that as needed. Thanks for pointing this out. I=E2=80=99ll split the two lifetime models. For v3 I=E2=80=99ll keep the = existing request_firmware_nowait() semantics and add only an explicit cancel/sync = path for callers that manage teardown manually. That should cover the TAS2781 case without making the existing API implic= itly devres-managed. If a managed variant is useful, it can be added separatel= y as devm_request_firmware_nowait() on top of the explicit cancel path. I=E2=80=99ll also avoid the devres_add() / schedule_work() ordering issue= in the current version. --=20 Thanks, C=C3=A1ssio --------------aV2TDdxkkyQRlrI9J4ccR6AJ-- --------------YGdOVAJBVEA1TPH3T13ph9kG Content-Type: application/pgp-signature; name="OpenPGP_signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="OpenPGP_signature.asc" -----BEGIN PGP SIGNATURE----- wnsEABYIACMWIQSrYqI5vIrg1X9eqEjQXT8aWv/ugwUCafQd6QUDAAAAAAAKCRDQXT8aWv/ug+RH AP9HQg53zZJFnXm7+M5h8QCkDPtpDeepvobxBCADZe8uSwEAt0sk2q2cf9VilZUUkqneF3Bmy+LY vffG7i2is5U9zgM= =pMut -----END PGP SIGNATURE----- --------------YGdOVAJBVEA1TPH3T13ph9kG--