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 4E503DDC5 for ; Mon, 20 Oct 2025 15:39:14 +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=1760974756; cv=none; b=YIAerN+kGgOHCPyyuM1K6j2aFRnKMyfrJ2ldkzKABvjrBht+axlOfoRv0HLNyx/edjJiVuOf0qq4+sqfapst73EgR6X+sjc1hoSvtOfakHSHSekqWyO6TRTlln8l2NhS0xKg/gZWKQmY19O0SM5eOD21+JEnAEhVw+lBglpmiQM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760974756; c=relaxed/simple; bh=GbuxPeQMwS9oGj90SYOXOii9DWOCB/BYzH4BmGZssnE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ryhw0wD6fHH0V1ltzLhGRtxMxbhbdRX1+0zBUjqfSnfdg3tCphX27Pyjhl5bC2GQ7Lh5L8zNZaFea5DubhEgO2+4t8GvGyVRTTP7AZziOJAQTfBlb1ZXa19TwaEVMROybhbeSlwvSo8hWM5d1xRLIrjoznJ/LX2oNSiKYVFFcLs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ghuFIDao; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="ghuFIDao" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4005CC4CEF9; Mon, 20 Oct 2025 15:39:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1760974754; bh=GbuxPeQMwS9oGj90SYOXOii9DWOCB/BYzH4BmGZssnE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ghuFIDao5bRaHw4TQts6ItytJlGbCdh2IM2643jFXw1h2PJicrtczAnqY0+zmIqx5 FgBajXH48nkIz4B6jNojcp0Marlbjx+L+rdKfpHMd1LSTQWdjJm0tb4+EdrCgRo83L ze2wAG+s4RAlGzpkpxJIhiaE6tHPPRn8RDv+KDgOi+1gcet+L3hneFhkC820eX2Boi UmTm9wt8GNvbyxTm0M0M5zm8BGAwCgdlMayN2rtu5G9btQDKmbkRucOWOzkjtfxM9v f3/DHoFv9G5FH1q5l7DAUz/kWb1e5AaYr3nC5AhzUWGBZCMZDVuZlErCMr5Aq8WMNS oqFovTVoCcGvQ== From: Sasha Levin To: stable@vger.kernel.org Cc: Xiao Liang , Herbert Xu , Sasha Levin Subject: [PATCH 6.1.y] padata: Reset next CPU when reorder sequence wraps around Date: Mon, 20 Oct 2025 11:39:11 -0400 Message-ID: <20251020153911.1821042-1-sashal@kernel.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <2025101650-dreamless-dry-49d5@gregkh> References: <2025101650-dreamless-dry-49d5@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Xiao Liang [ Upstream commit 501302d5cee0d8e8ec2c4a5919c37e0df9abc99b ] When seq_nr wraps around, the next reorder job with seq 0 is hashed to the first CPU in padata_do_serial(). Correspondingly, need reset pd->cpu to the first one when pd->processed wraps around. Otherwise, if the number of used CPUs is not a power of 2, padata_find_next() will be checking a wrong list, hence deadlock. Fixes: 6fc4dbcf0276 ("padata: Replace delayed timer with immediate workqueue in padata_reorder") Cc: Signed-off-by: Xiao Liang Signed-off-by: Herbert Xu [ applied fix in padata_find_next() instead of padata_reorder() ] Signed-off-by: Sasha Levin --- kernel/padata.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/kernel/padata.c b/kernel/padata.c index b3f79f23060c1..d49f97abe086f 100644 --- a/kernel/padata.c +++ b/kernel/padata.c @@ -282,7 +282,11 @@ static struct padata_priv *padata_find_next(struct parallel_data *pd, if (remove_object) { list_del_init(&padata->list); ++pd->processed; - pd->cpu = cpumask_next_wrap(cpu, pd->cpumask.pcpu, -1, false); + /* When sequence wraps around, reset to the first CPU. */ + if (unlikely(pd->processed == 0)) + pd->cpu = cpumask_first(pd->cpumask.pcpu); + else + pd->cpu = cpumask_next_wrap(cpu, pd->cpumask.pcpu, -1, false); } spin_unlock(&reorder->lock); -- 2.51.0