From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 D51591E89C for ; Tue, 9 Sep 2025 06:45:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757400340; cv=none; b=u+IG4rVljHY8GsFu3cwrPTxTribgqR2hdp8rgvMr8M3ctBofVWsriBqGQ7w0Y+2EJtyGl997V7oLVeTSX/fjDw54S33mSXFDCBBkM7z9Ais1hUiRvyKNM9lz7F2Bg/TPKDktxI9uRyljJbvnd7LitIwEW7f29p9UrUhZt30mrDI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757400340; c=relaxed/simple; bh=HLZgK+2vlCiBP60mDvIVPOoawJTagdQYNCgaZ6xCvSY=; h=Date:To:From:Subject:Message-Id; b=bKaXf1LVtdkaUn8YAh7SIj34d3hOBApd07MmZOUkLDGEkNCFCVUzMqaZ2TmkEMft/JfxK0PAzohyWdSWWmQdshGC5TIMRCB2ASJhBLfElLI1u1FsObmdZy18Wc38iiMOlpYljL+u6VD75BR+sz8FMhVeeJg5/CDqZJMB/Mpp2Hw= 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=zWZ8ei6w; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="zWZ8ei6w" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 525D8C4CEF4; Tue, 9 Sep 2025 06:45:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1757400340; bh=HLZgK+2vlCiBP60mDvIVPOoawJTagdQYNCgaZ6xCvSY=; h=Date:To:From:Subject:From; b=zWZ8ei6wnX1+EIvz0wXZhSrQeB8XWuCS/fBiX6Z3avgbgZA5IohZbLAVIeTD8RWrS Tj4+xEYqH6bPpB9vfuFzOJL7+WeR2eLl8K5QF0vOQmQHToMNdvjKTS2DxJ+V7i19+6 ShVcjCAdM52UmPbmSKAmlLdw6I1noz52g3JjWx8k= Date: Mon, 08 Sep 2025 23:45:39 -0700 To: mm-commits@vger.kernel.org,tj@kernel.org,dennis@kernel.org,cl@gentwo.org,bhe@redhat.com,vdumitrescu@nvidia.com,akpm@linux-foundation.org From: Andrew Morton Subject: [merged mm-hotfixes-stable] percpu-fix-race-on-alloc-failed-warning-limit.patch removed from -mm tree Message-Id: <20250909064540.525D8C4CEF4@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The quilt patch titled Subject: percpu: fix race on alloc failed warning limit has been removed from the -mm tree. Its filename was percpu-fix-race-on-alloc-failed-warning-limit.patch This patch was dropped because it was merged into the mm-hotfixes-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm ------------------------------------------------------ From: Vlad Dumitrescu Subject: percpu: fix race on alloc failed warning limit Date: Fri, 22 Aug 2025 15:55:16 -0700 The 'allocation failed, ...' warning messages can cause unlimited log spam, contrary to the implementation's intent. The warn_limit variable is accessed without synchronization. If more than threads enter the warning path at the same time, the variable will get decremented past 0. Once it becomes negative, the non-zero check will always return true leading to unlimited log spam. Use atomic operation to access warn_limit and change condition to test for non-negative (>= 0) - atomic_dec_if_positive will return -1 once warn_limit becomes 0. Continue to print disable message alongside the last warning. While the change cited in Fixes is only adjacent, the warning limit implementation was correct before it. Only non-atomic allocations were considered for warnings, and those happened to hold pcpu_alloc_mutex while accessing warn_limit. [vdumitrescu@nvidia.com: prevent warn_limit from going negative, per Christoph Lameter] Link: https://lkml.kernel.org/r/ee87cc59-2717-4dbb-8052-1d2692c5aaaa@nvidia.com Link: https://lkml.kernel.org/r/ab22061a-a62f-4429-945b-744e5cc4ba35@nvidia.com Fixes: f7d77dfc91f7 ("mm/percpu.c: print error message too if atomic alloc failed") Signed-off-by: Vlad Dumitrescu Reviewed-by: Baoquan He Cc: Christoph Lameter (Ampere) Cc: Dennis Zhou Cc: Tejun Heo Signed-off-by: Andrew Morton --- mm/percpu.c | 20 ++++++++++++-------- 1 file changed, 12 insertions(+), 8 deletions(-) --- a/mm/percpu.c~percpu-fix-race-on-alloc-failed-warning-limit +++ a/mm/percpu.c @@ -1734,7 +1734,7 @@ void __percpu *pcpu_alloc_noprof(size_t bool is_atomic; bool do_warn; struct obj_cgroup *objcg = NULL; - static int warn_limit = 10; + static atomic_t warn_limit = ATOMIC_INIT(10); struct pcpu_chunk *chunk, *next; const char *err; int slot, off, cpu, ret; @@ -1904,13 +1904,17 @@ fail_unlock: fail: trace_percpu_alloc_percpu_fail(reserved, is_atomic, size, align); - if (do_warn && warn_limit) { - pr_warn("allocation failed, size=%zu align=%zu atomic=%d, %s\n", - size, align, is_atomic, err); - if (!is_atomic) - dump_stack(); - if (!--warn_limit) - pr_info("limit reached, disable warning\n"); + if (do_warn) { + int remaining = atomic_dec_if_positive(&warn_limit); + + if (remaining >= 0) { + pr_warn("allocation failed, size=%zu align=%zu atomic=%d, %s\n", + size, align, is_atomic, err); + if (!is_atomic) + dump_stack(); + if (remaining == 0) + pr_info("limit reached, disable warning\n"); + } } if (is_atomic) { _ Patches currently in -mm which might be from vdumitrescu@nvidia.com are