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Thu, 16 Jan 2025 08:37:52 +0000 (GMT) Message-ID: <7ce44659-60a6-4647-bb74-fb6017ceb129@linux.ibm.com> Date: Thu, 16 Jan 2025 14:07:51 +0530 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: sched: Clarify PREEMPT is full preemption model To: =?UTF-8?B?5L2Z5Y2O5YW1?= Cc: "linux-kernel@vger.kernel.org" , "mingo@redhat.com" , "peterz@infradead.org" References: From: Shrikanth Hegde Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: bCqrwh89oieQY1eEAQrxsYVKtGo2PQg4 X-Proofpoint-ORIG-GUID: bCqrwh89oieQY1eEAQrxsYVKtGo2PQg4 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1057,Hydra:6.0.680,FMLib:17.12.68.34 definitions=2025-01-16_03,2025-01-16_01,2024-11-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 impostorscore=0 spamscore=0 malwarescore=0 lowpriorityscore=0 mlxscore=0 suspectscore=0 priorityscore=1501 bulkscore=0 mlxlogscore=999 clxscore=1011 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2411120000 definitions=main-2501160061 Please use plaintext for sending mail containing patches. Not able to see the patch on my mail client. Also the text is not formatted. https://docs.kernel.org/process/submitting-patches.html#no-mime-no-links-no-compression-no-attachments-just-plain-text On 1/15/25 15:24, 余华兵 wrote: > The configuration file "kernel/Kconfig. preempt" says that PREEMPT_RT is > fully preemptible, but from the function preempt_model_full() it can be > seen that PREEMPT is full preemption model. -------------------------- > kernel/Kconfig.preempt config PREEMPT         bool "Preemptible Kernel > (Low-Latency Desktop)" config PREEMPT_RT         bool "Fully Preemptible > Kernel (Real-Time)" include/linux/preempt.h static inline bool > preempt_model_full(void) {         return IS_ENABLED(CONFIG_PREEMPT); } > -------------------------- On Preempt_RT kernel, the spinlocks are sleeping locks and irqs can run as threaded. So even those can be preempted if necessary. That is not true with preempt=full alone. I suggest that the configuration file > "kernel/Kconfig. preempt" should be consistent with the function > preempt_model_full(). Modify the file "kernel/Kconfig.preempt" as > follows. ------------------ config PREEMPT         bool "Fully > Preemptible Kernel (Low-Latency Desktop)" config PREEMPT_RT         bool > "Real-time Kernel" ------------------