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 EB0661844B5; Tue, 7 May 2024 23:14:33 +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=1715123674; cv=none; b=OHVroCJo9N2KYh54k8dD9/0Xwadz5eky5iNcBjvu2XJvt+2kpbqqQSOpqBng7AAOuhX1PSM3tdizC8PmXCfFlTRuQzbd6Xz8pAT5kce9qNAm92fizQVgeT86VRGpourktjqFbHZj/4e4+BWxUOwTyflHUDv/pVUtlxpgEynXAQM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1715123674; c=relaxed/simple; bh=uGaz81u//ikxr+CCjdWRrcxgzw6GnAiHPyHKN2atUig=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=WeXv0dfOeTBMsUY1SRwH4FtyRTFZma9HSNMcHxedAhBmTYo/co3QR7xHUV7tp2IcUffKdf5Ixwy5zAF0jE9dK87zpQghaZqxMrwx5o80kR+5rQq7j7sbUgIWzLdW5klrF1QUDgMGkMyomBemQRrdg2kguBdr17uGIlNHEjLCYr0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=SBzBCNkQ; 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="SBzBCNkQ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id F026DC4AF17; Tue, 7 May 2024 23:14:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1715123673; bh=uGaz81u//ikxr+CCjdWRrcxgzw6GnAiHPyHKN2atUig=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=SBzBCNkQs2bocHhupLvuKIr+bQ2a05qDl1vhlaBlY9OEgj6082hD5QksQNyYkUilH qY9R7y++b05zxHaYUoYjuZGkBpPapMXcy+tyP5MJWUx4gcTxpTiw0gmk/iwIAHhCtS cw4weMLvtBmXJfMSCdKmEgZCyAumIUQ5n6TadJwznRzv3Rv8Ho4zQ6kABNf7OhBRTk dIVd9ShZMxR3K+64Q42DdGbh4xn9jCpyJVxLLZxNs2/gwDTzKNsadqwJf54o+3wkqk OMJystvlTwDMchZMw/IxjL2bT9a2H3B39ZonzYPueM+/nd4z6yHMJpTqah4QxF0lWJ qe7eWJA6Jt7lA== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Lancelot SIX , Felix Kuehling , Alex Deucher , Sasha Levin , Felix.Kuehling@amd.com, christian.koenig@amd.com, Xinhui.Pan@amd.com, airlied@gmail.com, daniel@ffwll.ch, amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org Subject: [PATCH AUTOSEL 5.4 5/6] drm/amdkfd: Flush the process wq before creating a kfd_process Date: Tue, 7 May 2024 19:14:21 -0400 Message-ID: <20240507231424.395315-5-sashal@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240507231424.395315-1-sashal@kernel.org> References: <20240507231424.395315-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore X-stable-base: Linux 5.4.275 Content-Transfer-Encoding: 8bit From: Lancelot SIX [ Upstream commit f5b9053398e70a0c10aa9cb4dd5910ab6bc457c5 ] There is a race condition when re-creating a kfd_process for a process. This has been observed when a process under the debugger executes exec(3). In this scenario: - The process executes exec. - This will eventually release the process's mm, which will cause the kfd_process object associated with the process to be freed (kfd_process_free_notifier decrements the reference count to the kfd_process to 0). This causes kfd_process_ref_release to enqueue kfd_process_wq_release to the kfd_process_wq. - The debugger receives the PTRACE_EVENT_EXEC notification, and tries to re-enable AMDGPU traps (KFD_IOC_DBG_TRAP_ENABLE). - When handling this request, KFD tries to re-create a kfd_process. This eventually calls kfd_create_process and kobject_init_and_add. At this point the call to kobject_init_and_add can fail because the old kfd_process.kobj has not been freed yet by kfd_process_wq_release. This patch proposes to avoid this race by making sure to drain kfd_process_wq before creating a new kfd_process object. This way, we know that any cleanup task is done executing when we reach kobject_init_and_add. Signed-off-by: Lancelot SIX Reviewed-by: Felix Kuehling Signed-off-by: Alex Deucher Signed-off-by: Sasha Levin --- drivers/gpu/drm/amd/amdkfd/kfd_process.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_process.c b/drivers/gpu/drm/amd/amdkfd/kfd_process.c index aa0a617b8d445..662e4d973f13a 100644 --- a/drivers/gpu/drm/amd/amdkfd/kfd_process.c +++ b/drivers/gpu/drm/amd/amdkfd/kfd_process.c @@ -289,6 +289,14 @@ struct kfd_process *kfd_create_process(struct file *filep) if (process) { pr_debug("Process already found\n"); } else { + /* If the process just called exec(3), it is possible that the + * cleanup of the kfd_process (following the release of the mm + * of the old process image) is still in the cleanup work queue. + * Make sure to drain any job before trying to recreate any + * resource for this process. + */ + flush_workqueue(kfd_process_wq); + process = create_process(thread); if (IS_ERR(process)) goto out; -- 2.43.0