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Sun, 11 Jul 2021 02:12:31 -0700 (PDT) Date: Sun, 11 Jul 2021 18:12:23 +0900 From: William Breathitt Gray To: David Lechner Cc: Jarkko Nikula , jic23@kernel.org, linux-stm32@st-md-mailman.stormreply.com, kernel@pengutronix.de, a.fatoum@pengutronix.de, kamel.bouhara@bootlin.com, gwendal@chromium.org, alexandre.belloni@bootlin.com, linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, syednwaris@gmail.com, patrick.havelange@essensium.com, fabrice.gasnier@st.com, mcoquelin.stm32@gmail.com, alexandre.torgue@st.com, o.rempel@pengutronix.de Subject: Re: [PATCH v12 15/17] counter: Implement events_queue_size sysfs attribute Message-ID: References: <1a624011-0b43-ac42-be53-a42f81923e5a@linux.intel.com> MIME-Version: 1.0 In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210711_021233_526684_AEC95C92 X-CRM114-Status: GOOD ( 20.46 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: multipart/mixed; boundary="===============4765143541546518626==" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org --===============4765143541546518626== Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="QSOFuI5CHXQO+dHV" Content-Disposition: inline --QSOFuI5CHXQO+dHV Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Sat, Jul 10, 2021 at 10:43:22AM -0500, David Lechner wrote: > On 7/10/21 5:25 AM, William Breathitt Gray wrote: > >> and after that > >> > >> [ 16.564403] =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D > >> [ 16.570725] WARNING: lock held when returning to user space! > >> [ 16.577044] 5.13.0-next-20210706+ #4 Not tainted > >> [ 16.582198] ------------------------------------------------ > >> [ 16.588507] cat/331 is leaving the kernel with locks still held! > >> [ 16.595214] 1 lock held by cat/331: > >> [ 16.599103] #0: ffff888102bb3630 > >> (&counter->chrdev_lock){+.+.}-{3:3}, at: counter_chrdev_open+0x21/0x60 > >> [counter] > >> > >> Jarkko > > I'm not sure how to resolve this warning. The purpose of this lock is to > > limit chrdev to a single open at a time. To accomplish this I grab this > > lock in counter_chrdev_open() and hold it until counter_chrdev_release() > > is called. Is there a better way to accomplish this? >=20 > How about using an atomic flag, e.g test_and_set_bit()? Yes, I think this might work: atomically test and set the bit to lock and atomically clear it to unlock. I'll replace the mutex with an atomic flag. By the way, what is the difference between test_and_set_bit() and test_and_set_bit_lock()? William Breathitt Gray --QSOFuI5CHXQO+dHV Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAABCgAdFiEEk5I4PDJ2w1cDf/bghvpINdm7VJIFAmDqtfcACgkQhvpINdm7 VJJoJw/8DNxxfECJciiVQx9aysjKNMY0qReiNt0Ua1DGfW7g2h9MFwl+YZo/NqN0 JySbFvJ4DHIeUed1KOfr7bH4J0/PEG20xbEO14wHUyWBehXomn5/67lrDnzJ82Px ih54U7JEEqdoda6eswt3U1dkvCwJF9lOzQDLe4xLFy127I/bctSDVncYpbFRcYlJ VHf6EuD4Tu30IGYhLbDWIrZgv+nMXWzpx4m0cUPFhFJO2oW83GSYVKo0yB14NLJo lmfzrmoX+9SPI3LLiu47yphY2nKSfvvb7Wi+ScOnUSvDd9a43Tb51tiZGoobbgGa pWu5WXPnNcR5XYmIXx2vxxWx7XLAR+mxW85VO2MeQGQtsbiFeGUHuvbexqAu3JeA EC6wySkTB35hgaesvsJMsBNfGdlQZjzydIidJqK0/uKEfqTL0+wJrnq5YsSkJ//o DSRjEZor8+mYj6rDHLH2AIZRUKA7ddqzZWII693FJ6075iMWW2ptqznPx1ln/uiB kXD3tuAuOv0fN4J7FJ+pOBWSszVUOIV26CoidHSmWXAKjdrx7HAwuYCgI/TaIgsy G971rJubdTI0t/G1LOmQh0QvRcqeSiaOjMK8kbF1XGEJcRAOGM2ih8klUCZhDt6r UyvmHW85UUQly1l4G7vtXa6X0cQ8sckFlwEQz1kjP/i3HAP/qbo= =Lh1x -----END PGP SIGNATURE----- --QSOFuI5CHXQO+dHV-- --===============4765143541546518626== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel --===============4765143541546518626==--