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Assume this Is the latest. >> https://git.kernel.org/pub/scm/linux/kernel/git/tglx/devel.git/ rseq/ >> slice >> >> Appears to be spinning in mm_get_cid(). Must be the mm cid changes. >> https://lore.kernel.org/all/20251029123717.886619142@linutronix.de/ > > When this happened during the development of the "complex" mm_cid > scheme, this was typically caused by a stale "mm_cid" being kept around > by a task even though it was not actually scheduled, thus causing > over-reservation of concurrency IDs beyond the max_cids threshold. This > ends up looping in: > > static inline unsigned int mm_get_cid(struct mm_struct *mm) > { >         unsigned int cid = __mm_get_cid(mm, READ_ONCE(mm- > >mm_cid.max_cids)); > >         while (cid == MM_CID_UNSET) { >                 cpu_relax(); >                 cid = __mm_get_cid(mm, num_possible_cpus()); >         } >         return cid; > } > > Based on the stacktrace you provided, it seems to happen within > sched_mm_cid_fork() within copy_process, so perhaps it's simply an > initialization issue in fork, or an issue when cloning a new thread ? One possible issue here: I note that kernel/sched/core.c:mm_init_cid() misses the following initialization: mm->mm_cid.transit = 0; Thanks, Mathieu > > Thanks, > > Mathieu > -- Mathieu Desnoyers EfficiOS Inc. https://www.efficios.com