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[184.162.17.197]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-720ac16e418sm27710586d6.4.2025.09.03.04.31.07 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 03 Sep 2025 04:31:07 -0700 (PDT) Date: Wed, 03 Sep 2025 07:31:05 -0400 From: =?ISO-8859-1?Q?Jean-Fran=E7ois_Lessard?= To: Andy Shevchenko CC: Andy Shevchenko , Geert Uytterhoeven , linux-kernel@vger.kernel.org Subject: =?US-ASCII?Q?Re=3A_=5BPATCH_4/5=5D_auxdisplay=3A_linedisp=3A_suppor?= =?US-ASCII?Q?t_attribute_attachment_to_auxdisplay_devices?= User-Agent: Thunderbird for Android In-Reply-To: References: <20250901020033.60196-1-jefflessard3@gmail.com> <20250901020033.60196-5-jefflessard3@gmail.com> <9223FFA5-2B0F-4A74-AFE2-CB7C9703CFAB@gmail.com> Message-ID: 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 Le 3 septembre 2025 06 h 18 min 18 s HAE, Andy Shevchenko a =C3=A9crit=C2=A0: >On Tue, Sep 02, 2025 at 01:37:52PM -0400, Jean-Fran=C3=A7ois Lessard wrot= e: >> Le 2 septembre 2025 06 h 18 min 24 s HAE, Andy Shevchenko a =C3=A9crit=C2=A0: >> >On Sun, Aug 31, 2025 at 10:00:28PM -0400, Jean-Fran=C3=A7ois Lessard w= rote: > >=2E=2E=2E > >> >> +static DEFINE_SPINLOCK(linedisp_attachments_lock); >> > >> >Why spin lock and not mutex? >>=20 >> The attachment list operations are extremely lightweight (just adding/r= emoving >> list entries), making spinlock the optimal choice because: >> - Very short critical sections: Only list traversal and pointer assignm= ents; >> avoids context switching overhead for brief operations >> - No sleeping operations: No memory allocation or I/O within locked sec= tions >> - Future-proof atomic context safety: Can be safely called from interru= pt >> handlers if needed > >To me it sounds like solving non-existing problem=2E I am sure we will se= e no >driver that tries to call this API in an atomic context=2E > Yeah, I should have skipped "Future-proof atomic context safety"=2E I don't see how attach/detach would be called from atomic context=2E Maybe to_linedisp(), but not in the current implementation anyway=2E