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Tue, 3 May 2022 07:41:53 +0000 Received: from VI1PR0401MB2526.eurprd04.prod.outlook.com ([fe80::8c82:19c5:ce96:491b]) by VI1PR0401MB2526.eurprd04.prod.outlook.com ([fe80::8c82:19c5:ce96:491b%4]) with mapi id 15.20.5206.024; Tue, 3 May 2022 07:41:53 +0000 Message-ID: <92cf40db-bb38-a85e-76bb-61e985947d20@suse.com> Date: Tue, 3 May 2022 09:41:51 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.8.0 Subject: Re: [PATCH v2 (resend)] media: imon: reorganize serialization Content-Language: en-US To: Tetsuo Handa , Oliver Neukum , Sean Young , Alan Stern , Mauro Carvalho Chehab CC: Jarod Wilson , syzbot , andreyknvl@google.com, linux-media@vger.kernel.org, linux-usb@vger.kernel.org, syzkaller-bugs@googlegroups.com References: <00000000000043b599058faf0145@google.com> <5a06c7f1-9a29-99e4-c700-fec3f09509d2@I-love.SAKURA.ne.jp> <62dddbb9-3053-f284-f9db-3beda5e8e951@I-love.SAKURA.ne.jp> <349f3e34-41ed-f832-3b22-ae10c50e3868@I-love.SAKURA.ne.jp> <21ffa07a-1bc1-cb1f-eef4-6c3a73953061@I-love.SAKURA.ne.jp> <6ab13405-b942-ddbe-c2de-dd193fe40795@suse.com> <1b7b9a2a-d52c-ff35-f32d-d22d7980a80f@I-love.SAKURA.ne.jp> From: Oliver Neukum In-Reply-To: <1b7b9a2a-d52c-ff35-f32d-d22d7980a80f@I-love.SAKURA.ne.jp> Content-Type: text/plain; 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Either the device is disconnected, then >> you'll go to 'exit' or the refcount will go back to something >0, won't = it? >> > (Step 0) Say, ictx->users is initially 1. > > (Step 1) display_open() increments via refcount_inc_not_zero(), now is 2. > > (Step 2) imon_disconnect() decrements via refcount_dec_and_test(), now is= 1. > > (Step 3) if retval !=3D 0, display_open() needs to undo (Step 1) via > refcount_dec_and_test(), now is 0. > > because imon_disconnect() can be called while display_open() is in progre= ss... > Hi, thank you. I did not think of error handling. You are correct. =C2=A0=C2=A0=C2=A0 Regards =C2=A0=C2=A0=C2=A0 =C2=A0=C2=A0=C2=A0 Oliver