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McKenney" , rcu@vger.kernel.org Subject: Re: [linus:master] [sched, x86] 476e8583ca: WARNING:at_kernel/rcu/update.c:#torture_sched_setaffinity Message-ID: <20241126143024.EKo6QfKL@linutronix.de> References: <202411252253.e39d77c6-lkp@intel.com> 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-Disposition: inline Content-Transfer-Encoding: quoted-printable In-Reply-To: <202411252253.e39d77c6-lkp@intel.com> On 2024-11-25 22:29:09 [+0800], kernel test robot wrote: > Hello, Hi, > by this commit, we see the config has below diff: >=20 > --- /pkg/linux/x86_64-randconfig-161-20241120/gcc-12/35772d627b55cc7fb4f3= 3bae57c564a25b3121a9/.config 2024-11-22 17:03:32.458344665 +0800 > +++ /pkg/linux/x86_64-randconfig-161-20241120/gcc-12/476e8583ca16eecec0a3= a28b6ee7130f4e369389/.config 2024-11-22 17:02:59.440805587 +0800 > @@ -121,9 +121,11 @@ CONFIG_BPF_UNPRIV_DEFAULT_OFF=3Dy > # end of BPF subsystem >=20 > CONFIG_PREEMPT_BUILD=3Dy > -CONFIG_PREEMPT_NONE=3Dy > +CONFIG_ARCH_HAS_PREEMPT_LAZY=3Dy > +# CONFIG_PREEMPT_NONE is not set > # CONFIG_PREEMPT_VOLUNTARY is not set > # CONFIG_PREEMPT is not set > +CONFIG_PREEMPT_LAZY=3Dy > # CONFIG_PREEMPT_RT is not set > CONFIG_PREEMPT_COUNT=3Dy > CONFIG_PREEMPTION=3Dy >=20 =E2=80=A6 > commit: 476e8583ca16eecec0a3a28b6ee7130f4e369389 ("sched, x86: Enable Laz= y preemption") =E2=80=A6 > runtime: 300s > test: cpuhotplug > torture_type: trivial =E2=80=A6 > [ 150.797530][ T445] ------------[ cut here ]------------ > [ 150.797915][ T445] torture_sched_setaffinity: sched_setaffinity(445) = returned -22 > [ 150.798353][ T445] WARNING: CPU: 0 PID: 445 at kernel/rcu/update.c:535 = torture_sched_setaffinity (kernel/rcu/update.c:535 (discriminator 3))=20 I've been staring at this, and this is actually fine. Your config changes =66rom CONFIG_PREEMPT_NONE to CONFIG_PREEMPT_LAZY which implies CONFIG_PREEMPTION. The trivial RCU test there does sched_setaffinity() while preemption is enabled and CPU-hotplug runs in the background. So you get what you expect either by an attempt to move to a CPU which is no longer valid or by getting migrated to another CPU in the middle of your operation. This is all fine. You need to update your config file or your test. Sebastian