From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3EA6A42E007 for ; Mon, 3 Aug 2026 18:11:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785780682; cv=none; b=vBOEziTy+WRGqvJJ9jEdEKwPU2fuBVenuOr26I/c0f8gsGxEARFmrkU2J5eAolf5/R1DUm6aqWqhE54ng15UC8p9E3qdKKEGyNsiPBEeuFxAfM4hxTapvfHlxl3k1jw8tE7uz/EnWKAKOHW6bZdtZx5POjXgmRWmBSaFhsSLVZo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785780682; c=relaxed/simple; bh=nw7XwTxCiu/GzWFO6ve2rmZttQmpgyZJ9lCqm3EW5eE=; h=Date:To:From:Subject:Message-Id; b=nFpmf8dcFm9ZTmJCpPNw5WKhvddxr63H1tAG1B1JBbR3QQrOrPqlwiat/1dhbTojOQN6ngpaH5VU4Q78TmZU3L+yiPw5LOgrxd3dkqw14vwtIogYFQF05x7QIL9VTC/A8PZfMj7scJ8D33dHFRzfCXysOitEbXlvosSh+sEv4vQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=ryaIEKNj; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="ryaIEKNj" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B1E6B1F000E9; Mon, 3 Aug 2026 18:11:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1785780680; bh=wVVMXMmbgf9AoNZYONgwageyj4uNnVPKD18zWzT9Hfc=; h=Date:To:From:Subject; b=ryaIEKNjj/IuqTIOpCtst2RfIzQpZxtq/ZUcpA52EHfaWVmenogAqdB4t5XI5lJJm 2Y5bR9AFXjqb3CwI1iRxnZLLnV98uScyBLVJevk1Zw+1T8ztNVv+hQ/npLAttixghJ wktsNGF4L0Wt5SRJIYClYehEJJRM2Mg9DD0LEKXI= Date: Mon, 03 Aug 2026 11:11:20 -0700 To: mm-commits@vger.kernel.org,xu.xin16@zte.com.cn,ieidus@redhat.com,david@kernel.org,chengming.zhou@linux.dev,xialonglong@kylinos.cn,akpm@linux-foundation.org From: Andrew Morton Subject: + mm-ksm-avoid-missing-ksmd-wakeups-in-ksm_enter.patch added to mm-new branch Message-Id: <20260803181120.B1E6B1F000E9@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: mm/ksm: avoid missing ksmd wakeups in ksm_enter has been added to the -mm mm-new branch. Its filename is mm-ksm-avoid-missing-ksmd-wakeups-in-ksm_enter.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-ksm-avoid-missing-ksmd-wakeups-in-ksm_enter.patch This patch will later appear in the mm-new branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Note, mm-new is a provisional staging ground for work-in-progress patches, and acceptance into mm-new is a notification for others take notice and to finish up reviews. Please do not hesitate to respond to review feedback and post updated versions to replace or incrementally fixup patches in mm-new. The mm-new branch of mm.git is not included in linux-next If a few days of testing in mm-new is successful, the patch will me moved into mm.git's mm-unstable branch, which is included in linux-next Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via various branches at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there most days ------------------------------------------------------ From: Longlong Xia Subject: mm/ksm: avoid missing ksmd wakeups in ksm_enter Date: Mon, 3 Aug 2026 23:21:15 +0800 __ksm_enter() decides whether ksmd needs a wakeup by checking if the mm slot list is empty before inserting the new slot. The empty check is currently outside ksm_mmlist_lock. Another CPU can remove the last slot and let ksmd go back to sleep after the unlocked check, while this CPU inserts a new slot and skips the wakeup based on the stale result. Take ksm_mmlist_lock before checking the list so the empty-to-nonempty transition and the insertion are observed as one critical section. Link: https://lore.kernel.org/20260803152115.3479919-1-xialonglong2025@163.com Fixes: 6e15838425ac ("ksm: keep quiet while list empty") Signed-off-by: Longlong Xia Cc: Chengming Zhou Cc: David Hildenbrand Cc: Izik Eidus Cc: Xu Xin Signed-off-by: Andrew Morton --- mm/ksm.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) --- a/mm/ksm.c~mm-ksm-avoid-missing-ksmd-wakeups-in-ksm_enter +++ a/mm/ksm.c @@ -3053,7 +3053,7 @@ int __ksm_enter(struct mm_struct *mm) { struct ksm_mm_slot *mm_slot; struct mm_slot *slot; - int needs_wakeup; + bool needs_wakeup; mm_slot = mm_slot_alloc(mm_slot_cache); if (!mm_slot) @@ -3061,10 +3061,9 @@ int __ksm_enter(struct mm_struct *mm) slot = &mm_slot->slot; + spin_lock(&ksm_mmlist_lock); /* Check ksm_run too? Would need tighter locking */ needs_wakeup = list_empty(&ksm_mm_head.slot.mm_node); - - spin_lock(&ksm_mmlist_lock); mm_slot_insert(mm_slots_hash, mm, slot); /* * When KSM_RUN_MERGE (or KSM_RUN_STOP), _ Patches currently in -mm which might be from xialonglong@kylinos.cn are mm-ksm-avoid-missing-ksmd-wakeups-in-ksm_enter.patch