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Fri, 5 Jun 2026 11:01:35 +0000 (GMT) Message-ID: <078b0276-4458-4320-b35f-f8802720f886@linux.ibm.com> Date: Fri, 5 Jun 2026 12:01:35 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] sched: Further restrict the preemption modes To: Sebastian Andrzej Siewior Cc: Peter Zijlstra , Douglas Freimuth , Christian Borntraeger , Ilya Leoshkevich , mingo@kernel.org, Thomas Gleixner , juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, clrkwllms@kernel.org, linux-kernel@vger.kernel.org, linux-rt-devel@lists.linux.dev, Linus Torvalds , linux-s390@vger.kernel.org, Matthew Rosato , Hendrik Brueckner , Marco Crivellari References: <20251219101502.GB1132199@noisy.programming.kicks-ass.net> <182f110b-ac63-4db4-8b01-0e841639bc39@linux.ibm.com> <08307223-88ad-4550-963e-5d1ee315023c@linux.ibm.com> <20260303115235.GQ1282955@noisy.programming.kicks-ass.net> <6c3fbb6d-d4e1-4984-b584-c067be844098@linux.ibm.com> <20260605105211.rZ8x7Hd5@linutronix.de> Content-Language: en-GB From: Ciunas Bennett In-Reply-To: <20260605105211.rZ8x7Hd5@linutronix.de> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNjA1MDEwMyBTYWx0ZWRfXyayp2yInpsQY v6zWKD3bB28Gz9Epq0D/QiF22S9fSUd3OU9iF0vnT50dnRi0/oNMlSUr8qeH13tYJ9fk/U4b6dr PgJiUdLRl05xt0+bFQk/gLkBwBgSwk3J1pQxEep7JgTz9dRLc52MLqmL55rmSIBzMiq29hSERE/ qA74QP1zaqNRkVAHo8T3wbhcusjrRI2LBGIIwwTThjlA+1z1z+ncwidvWNYAotRc3Zw+hpMPITN kd+vlgxhQx6kvYHhvZMVWXNu/20I5iTDEoSKy+hxbOOIE8CWq4IiT1XpAJ7vUu1gQwz7mGTpp0j gxKifsBE+9+BASzR8lnujIL9dEArMH+1AtQyg4PdWCIJmslpp19tllnhyeKzwBl9kAt8DXgaDvP yqNgPwpkO4n0t28OPWCB8LKRjAHqzsDtxPHA54uu0nzkxQ4iapjMD0/cZ7zhFZtkL+cCg3ME7Ld aMzyglPqs8enscpm4hg== X-Proofpoint-ORIG-GUID: pli3czyyzOmgaO2JdJ7PPgBFCp7pJ855 X-Authority-Analysis: v=2.4 cv=cOzQdFeN c=1 sm=1 tr=0 ts=6a22ac98 cx=c_pps a=aDMHemPKRhS1OARIsFnwRA==:117 a=aDMHemPKRhS1OARIsFnwRA==:17 a=IkcTkHD0fZMA:10 a=FelO9ux0wxsA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=Y2IxJ9c9Rs8Kov3niI8_:22 a=ACxPka3VRXSE_1752UsA:9 a=QEXdDO2ut3YA:10 a=zZCYzV9kfG8A:10 X-Proofpoint-GUID: 4BrJN-HU9S0WlB8qvKXpJJw11YyeJZhD X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.125,FMLib:17.12.100.49 definitions=2026-06-05_01,2026-05-28_03,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1011 impostorscore=0 lowpriorityscore=0 spamscore=0 bulkscore=0 malwarescore=0 phishscore=0 suspectscore=0 priorityscore=1501 adultscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2605210000 definitions=main-2606050103 >> delayed significantly before it gets CPU time. > > There is some work done by Marco to rework the API to explicitly state > if a per-CPU workqueue is mandatory _or_ if an CPU unbound workqueue can > be used instead. (Rather than having schedule_work() not knowing the > implications). Oh, that is good some work already being done here. I had a small patch ready to go, but possibly the solution needs to be more robust. - schedule_work(&irqfd->inject); + queue_work(system_dfl_wq, &irqfd->inject); > It seems that using an unbound worker would avoid the problem at hand, > correct? > > Sebastian Yeah, changing to an unbound kworker avoids the issue in any of the testing I have done. Ciunas