From patchwork Sat Apr 23 21:22:18 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Dan Williams X-Patchwork-Id: 12824684 Received: from mga06.intel.com (mga06b.intel.com [134.134.136.31]) (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 5FF757C for ; Sat, 23 Apr 2022 21:22:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1650748939; x=1682284939; h=subject:from:to:cc:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=tWkequjSYEh30bCG4fPlkdokflxW/XwwcXiDxXk3wWw=; b=ZLkL8bd7zu/z9JmRsQMuuejFr7DMXDUAZBV3v+PSQVY8Z8Ws81rtEqKw /B+ebigwfeppDi6Y4Ijw+sI1bgdoyQDrmnQV+tbR3sq7V/mVkzrqGHIDZ nOFyVrtpJAFW8jjjnxHHztcjmXyzG6AB/TTlG/9H2RyQUmI1/Lvyd5vCQ 6pEPc9athS88K3rjuUMY6hdZy8TQlA8pS3S38dA/6UZhIeKXQpyfb3GJG EVRyjaDb41oGbALWUJLhU3vXMcGwAN96OX3GJAaUowW55p99y5NIOa9up S26U7qVS223yBWUN0s5HQg5Z+eO1cdON6X1GFRu9isVxCdiS1u6PWVfMH w==; X-IronPort-AV: E=McAfee;i="6400,9594,10326"; a="325417699" X-IronPort-AV: E=Sophos;i="5.90,285,1643702400"; d="scan'208";a="325417699" Received: from orsmga007.jf.intel.com ([10.7.209.58]) by orsmga104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 23 Apr 2022 14:22:18 -0700 X-IronPort-AV: E=Sophos;i="5.90,285,1643702400"; d="scan'208";a="557009140" Received: from dwillia2-desk3.jf.intel.com (HELO dwillia2-desk3.amr.corp.intel.com) ([10.54.39.25]) by orsmga007-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 23 Apr 2022 14:22:18 -0700 Subject: [PATCH v4 8/8] nvdimm: Fix firmware activation deadlock scenarios From: Dan Williams To: linux-cxl@vger.kernel.org Cc: nvdimm@lists.linux.dev Date: Sat, 23 Apr 2022 14:22:18 -0700 Message-ID: <165074883800.4116052.10737040861825806582.stgit@dwillia2-desk3.amr.corp.intel.com> In-Reply-To: <165055523099.3745911.9091010720291846249.stgit@dwillia2-desk3.amr.corp.intel.com> References: <165055523099.3745911.9091010720291846249.stgit@dwillia2-desk3.amr.corp.intel.com> User-Agent: StGit/0.18-3-g996c Precedence: bulk X-Mailing-List: nvdimm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Lockdep reports the following deadlock scenarios for CXL root device power-management, device_prepare(), operations, and device_shutdown() operations for 'nd_region' devices: Reviewed-by: Ira Weiny --- Chain exists of: &nvdimm_region_key --> &nvdimm_bus->reconfig_mutex --> system_transition_mutex Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(system_transition_mutex); lock(&nvdimm_bus->reconfig_mutex); lock(system_transition_mutex); lock(&nvdimm_region_key); -- Chain exists of: &cxl_nvdimm_bridge_key --> acpi_scan_lock --> &cxl_root_key Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&cxl_root_key); lock(acpi_scan_lock); lock(&cxl_root_key); lock(&cxl_nvdimm_bridge_key); --- These stem from holding nvdimm_bus_lock() over hibernate_quiet_exec() which walks the entire system device topology taking device_lock() along the way. The nvdimm_bus_lock() is protecting against unregistration, multiple simultaneous ops callers, and preventing activate_show() from racing activate_store(). For the first 2, the lock is redundant. Unregistration already flushes all ops users, and sysfs already prevents multiple threads to be active in an ops handler at the same time. For the last userspace should already be waiting for its last activate_store() to complete, and does not need activate_show() to flush the write side, so this lock usage can be deleted in these attributes. Fixes: 48001ea50d17 ("PM, libnvdimm: Add runtime firmware activation support") Signed-off-by: Dan Williams --- Changes since v3: - Remove nvdimm_bus_lock() from all ->capability() invocations (Ira) drivers/nvdimm/core.c | 9 --------- 1 file changed, 9 deletions(-) diff --git a/drivers/nvdimm/core.c b/drivers/nvdimm/core.c index 144926b7451c..d91799b71d23 100644 --- a/drivers/nvdimm/core.c +++ b/drivers/nvdimm/core.c @@ -368,9 +368,7 @@ static ssize_t capability_show(struct device *dev, if (!nd_desc->fw_ops) return -EOPNOTSUPP; - nvdimm_bus_lock(dev); cap = nd_desc->fw_ops->capability(nd_desc); - nvdimm_bus_unlock(dev); switch (cap) { case NVDIMM_FWA_CAP_QUIESCE: @@ -395,10 +393,8 @@ static ssize_t activate_show(struct device *dev, if (!nd_desc->fw_ops) return -EOPNOTSUPP; - nvdimm_bus_lock(dev); cap = nd_desc->fw_ops->capability(nd_desc); state = nd_desc->fw_ops->activate_state(nd_desc); - nvdimm_bus_unlock(dev); if (cap < NVDIMM_FWA_CAP_QUIESCE) return -EOPNOTSUPP; @@ -443,7 +439,6 @@ static ssize_t activate_store(struct device *dev, else return -EINVAL; - nvdimm_bus_lock(dev); state = nd_desc->fw_ops->activate_state(nd_desc); switch (state) { @@ -461,7 +456,6 @@ static ssize_t activate_store(struct device *dev, default: rc = -ENXIO; } - nvdimm_bus_unlock(dev); if (rc == 0) rc = len; @@ -484,10 +478,7 @@ static umode_t nvdimm_bus_firmware_visible(struct kobject *kobj, struct attribut if (!nd_desc->fw_ops) return 0; - nvdimm_bus_lock(dev); cap = nd_desc->fw_ops->capability(nd_desc); - nvdimm_bus_unlock(dev); - if (cap < NVDIMM_FWA_CAP_QUIESCE) return 0;