Messages in this thread | | | Date | Tue, 2 Aug 2022 16:44:46 +0100 | From | Matthew Wilcox <> | Subject | Re: [PATCH] mm: ksm: fix data-race in __ksm_enter / run_store |
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On Tue, Aug 02, 2022 at 11:15:50PM +0800, Kefeng Wang wrote: > The ksm_run is alread protected by ksm_thread_mutex in run_store, we > could add this lock in __ksm_enter() to avoid the above issue.
I don't think this is a great fix. Why not protect the store with ksm_mmlist_lock? ie:
mutex_lock(&ksm_thread_mutex); wait_while_offlining(); if (ksm_run != flags) { + spin_lock(&ksm_mmlist_lock); ksm_run = flags; + spin_unlock(&ksm_mmlist_lock); if (flags & KSM_RUN_UNMERGE) { set_current_oom_origin(); err = unmerge_and_remove_all_rmap_items(); clear_current_oom_origin(); if (err) { + spin_lock(&ksm_mmlist_lock); ksm_run = KSM_RUN_STOP; + spin_unlock(&ksm_mmlist_lock); ...
(I also don't think this is a real bug, because the call to unmerge_and_remove_all_rmap_items() will "cure" the misplacement of items in the list, but there's value in shutting up the tools, I suppose)
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