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Mon, 2 Aug 2021 06:08:38 +0000 From: "Qin, Chao" To: John Ogness , Sebastian Andrzej Siewior CC: "linux-kernel@vger.kernel.org" , "linux-rt-users@vger.kernel.org" , "tglx@linutronix.de" , "rostedt@goodmis.org" , "mgross@linux.intel.com" , "Mei, Paul" , "Li, Lili" Subject: RE: [PREEMPT_RT][PATCH] printk: Enhance the condition check of msleep in pr_flush() Thread-Topic: [PREEMPT_RT][PATCH] printk: Enhance the condition check of msleep in pr_flush() Thread-Index: AQHXfEaHiU7PgYfePkWUMKzzHnOuTatKY8eAgBE6hoCAAAyRAIAEJD7Q Date: Mon, 2 Aug 2021 06:08:38 +0000 Message-ID: References: <20210719022649.3444072-1-chao.qin@intel.com> <87mtqiuzd4.fsf@jogness.linutronix.de> <20210730140143.53wls2g7xf2ktdgv@linutronix.de> <87k0l7svu5.fsf@jogness.linutronix.de> In-Reply-To: <87k0l7svu5.fsf@jogness.linutronix.de> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: dlp-version: 11.5.1.3 dlp-product: dlpe-windows dlp-reaction: no-action authentication-results: linutronix.de; 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charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: DM6PR11MB3802.namprd11.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: 97f2bf89-e6a7-4a06-95b2-08d9557bf842 X-MS-Exchange-CrossTenant-originalarrivaltime: 02 Aug 2021 06:08:38.3307 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 46c98d88-e344-4ed4-8496-4ed7712e255d X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: VEDWmjn2u9S+sfVHtrS7tUCjQ5K3kuyCb8clzNMmp1rvSCuu7jnticmtdG/+NpDv0BS8psmOkocaBDelNchvMA== X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM5PR11MB0025 X-OriginatorOrg: intel.com Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org As John Ogness commented, I also found it would hang if sleep when >=3D SYS= TEM_SCHEDULING. And as in commit https://lore.kernel.org/lkml/20170516184736.272225698@lin= utronix.de/, it should enable sleep right when the scheduler starts workin= g(>=3D SYSTEM_RUNNING). -Chao. -----Original Message----- From: John Ogness =20 Sent: Friday, July 30, 2021 10:47 PM To: Sebastian Andrzej Siewior Cc: Qin, Chao ; linux-kernel@vger.kernel.org; linux-rt-= users@vger.kernel.org; tglx@linutronix.de; rostedt@goodmis.org; mgross@linu= x.intel.com; Mei, Paul ; Li, Lili Subject: Re: [PREEMPT_RT][PATCH] printk: Enhance the condition check of msl= eep in pr_flush() On 2021-07-30, Sebastian Andrzej Siewior wrote: > On 2021-07-19 17:01:51 [+0206], John Ogness wrote: >> On 2021-07-19, chao.qin@intel.com wrote: >> > --- a/kernel/printk/printk.c >> > +++ b/kernel/printk/printk.c >> > @@ -3620,7 +3620,8 @@ bool pr_flush(int timeout_ms, bool reset_on_prog= ress) >> > u64 diff; >> > u64 seq; >> > =20 >> > - may_sleep =3D (preemptible() && !in_softirq()); >> > + may_sleep =3D (preemptible() && !in_softirq() >> > + && (system_state >=3D SYSTEM_RUNNING)); > > I don't have more context but scheduling should work starting with=20 > SYSTEM_SCHEDULING. I also thought this, but a quick test shows that is not the case. For examp= le, init/main.c:kernel_init() is called in preemptible context, but msleep() will hang if called at the beginning of that function. John Ogness