From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from stravinsky.debian.org (stravinsky.debian.org [82.195.75.108]) (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 E803124E4B4; Mon, 15 Jun 2026 17:49:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=82.195.75.108 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781545770; cv=none; b=rIkVzHA7PiFfcSG9n9Je/UeUsieS5Ls7X+HMEWMXePsCx1clltfX9APtITiDlbbR7s28oz2LkGq0WIu/0fHztqG2TrDNjgLUOxX4w4K8beMPis1/LHh3gJ++4N873sp3+jNAuCOL+hR8AWbFDKK5DWY4ZeQtLA70CBtwlG05F7g= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781545770; c=relaxed/simple; bh=pUQT9CsXT8CQUM/Dgn56GXDZkIOsLy2lpBqCJ8T2PEs=; h=From:Subject:Date:Message-Id:MIME-Version:Content-Type:To:Cc; b=sQNJQQuV1aGIB7vLd+UiZZWk+2tppJGiO0wXYBu3OQSNRUkB0BLFk1Pwup9AbdjsFhsjuypNrP80bzrvY1ggQptqTUs9zgFrysbt8AipNZTDXJytk21SCRUk6aAK2Zs5opWFgkA2x3k+rMRI58sRHGGMdLJqN6KTIjJVxD5W2Hc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=debian.org; spf=pass smtp.mailfrom=debian.org; dkim=pass (2048-bit key) header.d=debian.org header.i=@debian.org header.b=Nj8ARF20; arc=none smtp.client-ip=82.195.75.108 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=debian.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=debian.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=debian.org header.i=@debian.org header.b="Nj8ARF20" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=debian.org; s=smtpauto.stravinsky; h=X-Debian-User:Cc:To:Content-Transfer-Encoding: Content-Type:MIME-Version:Message-Id:Date:Subject:From:Reply-To:Content-ID: Content-Description:In-Reply-To:References; bh=5wvmPgyc9uvgveJA+YngPrzTpU2IXWeRQ7fyKgf6vHY=; b=Nj8ARF2067PXREHbUlqIJHoaAe YGdSpe8jfqxPP5JnJu0bDglAAZHWDB4Mq9VUu2+GJfsxZql3w+B4QE688kOuVCGitBKHxkZW09H6T cscGnH0OUrlk3nYloF0HmTaNbcjg44mdig8Q1kv9aVcol4H04EYOeEMMnFibFqiPsukSOa8YETwom yhMKc9GxJGUG1lko8XrX3BQZei28b896xmAfnhnd97O7S9TSCNOi9JgQRTcADukiIrf5i/MfMD4lH LGDvZKNqKnKCIFdEOTW70HszHlbwFbhLuKs1QsmjVpPLpxiyPN2fmQv5quxD6jwlh6V2v0emSyjKn kX3cUkeQ==; Received: from authenticated-user by stravinsky.debian.org with esmtpsa (TLS1.3:ECDHE_X25519__RSA_PSS_RSAE_SHA256__AES_256_GCM:256) (Exim 4.96) (envelope-from ) id 1wZBR4-00DFK1-1F; Mon, 15 Jun 2026 17:49:22 +0000 From: Breno Leitao Subject: [PATCH v3 0/3] mm/kmemleak: avoid soft lockup when scanning task stacks Date: Mon, 15 Jun 2026 10:49:05 -0700 Message-Id: <20260615-kmemleak-stack-resched-v3-0-acecd7d7fd92@debian.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-B4-Tracking: v=1; b=H4sIABE7MGoC/4XNyw6CMBBA0V9pZs2YdnhVVv6HcVHpAA3ySEsaD eHfDax0YdzexbkrBPaOA1RiBc/RBTeNUIk0EVB3ZmwZnYVKAEkqZKEU9gMPDzY9hsXUPXoOdcc WpWJbks61KRtIBMyeG/c84OstEdC5sEz+dXyi2utfMipUaAvKtLGcN5m5WL47M54m38JuRvp06 KdDqDBPKZOWyzNr/eVs2/YGBXSWSgUBAAA= X-Change-ID: 20260611-kmemleak-stack-resched-01ed72858a7f To: Catalin Marinas , Andrew Morton , lance.yang@linux.dev, Davidlohr Bueso , Oleg Nesterov , Qian Cai Cc: oleg@redhat.com, sj@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Breno Leitao , kernel-team@meta.com, stable@vger.kernel.org X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; a=openpgp-sha256; l=1715; i=leitao@debian.org; h=from:subject:message-id; bh=pUQT9CsXT8CQUM/Dgn56GXDZkIOsLy2lpBqCJ8T2PEs=; b=owEBbQKS/ZANAwAIATWjk5/8eHdtAcsmYgBqMDsepC4qV9HPAOcAmwK8L4No+fcaNcYc3M2f7 8G7+Mr5AcCJAjMEAAEIAB0WIQSshTmm6PRnAspKQ5s1o5Of/Hh3bQUCajA7HgAKCRA1o5Of/Hh3 beIoEACt/P86zHel9broPJBl8+3GHNLaWYYbBFpq+ykw9PWO6KYvjuO+UfsHa6mYOdvpTxkT+sK 7KqkG78hRw9qAgz/nvMoUa0R/E5bg8bUIJXUtUr0GjCgjLFg91gcQJqBqW+eoUa3AKhoLG6g18W Uwlnc8jzV5e3LVtWuZVQIyTU+YWeD1a/ZcwQqYIus9vlnAzTOEnZM/b92lqs3hHt9hE5RfG6f9x P/gn/56B096qeREstMBIEL1/YZ53Rpql86LLUgsZyL7xiANpGk+Asaiw+V0CbugYJx6BlXFEyCN Br2ePNIyOMBZBhzyMZoJHAYs+0GuOOcGysB6+HCOp43OetvB7dci2ac6U5/g0fOWcoLx9zeIZvF 7ZvE6aPIhiuW7TD7Gu0mtFLAKn0Z/e/RDR/0aPfW96SPI/Dwu2jFmTxbjyUqUmI02vZVQagQtmw 0jsZtwtuh9k2+vdp/LR9KugkM5V8LRRv05i9Tu/upv05kr3WH39r9B0NryVMSGfKMgJUKhtTSsd zug5dtJSujBwrNTZKVqC5wPz/sT59jXph2sP539gonJDwa8+uzh3k6+aXvvFatwq0sCgOSB0NLC Hi0fIXE9FBu3N7yQPFP8/9KPogcrJVPeLve2O2JrCGGTXZJSAYHSuTVJt60QWBzQsMc9lRKDp/N VvwJNnhIspXqeSA== X-Developer-Key: i=leitao@debian.org; a=openpgp; fpr=AC8539A6E8F46702CA4A439B35A3939FFC78776D X-Debian-User: leitao kmemleak_scan() scans every task stack under one rcu_read_lock() with no reschedule point, which can trip the soft lockup watchdog on hosts with very many threads. That prints the following message, depending on the workload+host configuration: watchdog: BUG: soft lockup - CPU#35 stuck for 22s! [kmemleak:537] scan_block kmemleak_scan kmemleak_scan_thread kthread Patch 1 walks the tasks with find_ge_pid() so the scan reschedules between tasks Patches 2-3 let the scan loops stop early once a scan is interrupted. Signed-off-by: Breno Leitao --- Changes in v3: - Rework the task stack walk to use find_ge_pid() instead of v1's array and v2's rcu_lock_break() helper (Catalin). - Add two follow-up patches letting scan_block() report an interrupted scan so the scan loops stop early. - Link to v2: https://lore.kernel.org/r/20260612-kmemleak-stack-resched-v2-1-53240de79e88@debian.org Changes in v2: - Do not create the nasty array, but use the same pattern as kernel/hung_task.c. - Link to v1: https://lore.kernel.org/r/20260611-kmemleak-stack-resched-v1-1-d6248ade5f4a@debian.org --- Breno Leitao (3): mm/kmemleak: avoid soft lockup when scanning task stacks mm/kmemleak: stop the task stack scan early when interrupted mm/kmemleak: stop the per-cpu and struct page scans early too mm/kmemleak.c | 88 +++++++++++++++++++++++++++++++++++++++++++---------------- 1 file changed, 65 insertions(+), 23 deletions(-) --- base-commit: abe651837cb394f76d738a7a747322fca3bf17ba change-id: 20260611-kmemleak-stack-resched-01ed72858a7f Best regards, -- Breno Leitao