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definitions=main-2311090002 X-Proofpoint-GUID: dykLzYEMtp3w-82WHufAuFtjfhxCCsTE X-Proofpoint-ORIG-GUID: dykLzYEMtp3w-82WHufAuFtjfhxCCsTE X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 2D3DDA000F X-Stat-Signature: 5eyme4c9wnzu4h9h3ztgkbai5z1z53an X-Rspam-User: X-HE-Tag: 1699490145-784686 X-HE-Meta: U2FsdGVkX1/2sTbtGCM5cyaQMXw8QBCLJNZXSyLKVg+8lLGF0J3HscjIXgz/9vKpxF5zI4nn+lBjPifwNCp0/efQyVcaJEDl3FHpedg5Qi4yBlyNUCarjl4Fva8VUDBaiJb2hgOZ2NBPk0zrnpmp0jYr4z6tg48yuxwIkXzjBylxl2XAdUV6YwLH8avTuSWgaOpd7xdlXwontg0obeLZDUJep9Fs2sDasLfrgW5DqXk6OgzOVPH9/ZvjXo+BRYpOoBsV0KT/mXWAl4ETSHcqdDCrua9eYD7gQEQrGhXZv9eHQzKkApnRludBDTQ3Ixehg+Mx4X2KjLq/C+JNr9UrqCtEuF81+WIM7B3FnLk6uldpshuidhwm7rw/aZYD8PHzTdVV4/0ZWqlwqvITJlRRe4a/KrSaUdVD3ePqVD5KUI576c0JpczsKb3kEicpVO5Uu/lzARIjv+Hr/NzX8UhVvYSIUCFf4gUR02/68RBHGGlO7bteAqZl2Ku0k/bRE/CiITUCH5op+yV3y3TZN5gD3VExXaTV6UVxAaCDRYWqwa2lwBYod/xJKeke+IZkn42woVPc+9nmvC9w3meR8/gu1W6dRwXOWa7bMyvSwJMV14gqcI/8LPTRh27JwhHcMWnpJYdAwJc04+dlEdvoF4bRC6Lj3tg8KFra53CLYytyjlsCOH9xSUIzFen9Fx7ebeFZqiKRCDySJso1I1Xa2zrEmUrUE/cV4EJP7dY8HuZ9UakJrrfVGa0QOG4lHWoWzUA8Pm3/WejmFwj+Hp8+ZTfAr0rucCxCftDwQCFP/3EtCvB3fN1DpV9/I8RoFd80K4PtPWutHMTMYqed9FXCrWhc98dCm1v+UmiETuPzQxN0bf3fDffTSH9jd7y2Tx55hChK1ro1F6HNJ282/e7AspopIwmLwIocON4nz1Vr8z92bLD+NybOG6tCCbJpwY0Yjbu3Blxm5tkJx4zUXAGtNRq SY3kY2bP v1ocmYJw3YkSeWZN5iz3TeE6eR6IrXt2HPdhH22eKqK99F3yyy5fF1k5dURAtIAKF9IY2ridjOYZpf8wEcC4LDkZirA8iwe3iHXSzyCHq1SUrKoHLgll8sAuejrglGLjqPlopJEXpNFC9CUvijT1xue+vtr24jQBgYlqxBmmD5KKvkpeuByDnURmmjTmQ4v/RLluY+sYDnRZOYACkaqsEpRe7AkWUBlFbq0Zn7fqYDV9Sb3AUOD3YSCH0ICfVpnm2/MtDzCKP8ENMFSfMUusU3/Ds5H4fyPWRuPUiMS8KzsosqKkORR9MGECciXkjJFlHUnsNzIMyGf7ZU/zpA28oaYP1+BJiFmMmYYxIwBV2OWLdKK3rtBq0kUeBNkIxusyEgEQAYc52+W2UklmcGRRexfHJ/ZDyC60ysAobxCRe0nrdQG/5xgXRMYL+jRXLWHDILYIcZt1e9Ux/Q3iSlCAbFpHTXeLnsgKyF8EI X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Mark Rutland writes: > On Tue, Nov 07, 2023 at 01:56:46PM -0800, Ankur Arora wrote: >> What's broken: >> - ARCH_NO_PREEMPT (See patch-45 "preempt: ARCH_NO_PREEMPT only preempts >> lazily") >> - Non-x86 architectures. It's trivial to support other archs (only need >> to add TIF_NEED_RESCHED_LAZY) but wanted to hold off until I got some >> comments on the series. >> (From some testing on arm64, didn't find any surprises.) > > When you say "testing on arm64, didn't find any surprises", I assume you mean > with an additional patch adding TIF_NEED_RESCHED_LAZY? Yeah. And, handling that in the user exit path. > Note that since arm64 doesn't use the generic entry code, that also requires > changes to arm64_preempt_schedule_irq() in arch/arm64/kernel/entry-common.c, to > handle TIF_NEED_RESCHED_LAZY. So, the intent (which got muddied due to this overly large series) was to delay handling TIF_NEED_RESCHED_LAZY until we are about to return to user. I think arm64_preempt_schedule_irq() should only handle TIF_NEED_RESCHED and the _TIF_NEED_RESCHED_LAZY should be handled via _TIF_WORK_MASK and do_notify_resume(). (The design is much clearer in Thomas' PoC: https://lore.kernel.org/lkml/87jzshhexi.ffs@tglx/) >> - ftrace support for need-resched-lazy is incomplete > > What exactly do we need for ftrace here? Only support for TIF_NEED_RESCHED_LAZY which should be complete. That comment was based on a misreading of the code. Thanks -- ankur