From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 1445AC19F4F for ; Tue, 7 May 2024 23:11:59 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 6E1AC112FFF; Tue, 7 May 2024 23:11:58 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.b="WHiKDmEy"; dkim-atps=neutral Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by gabe.freedesktop.org (Postfix) with ESMTPS id 102C5112FFD; Tue, 7 May 2024 23:11:57 +0000 (UTC) Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by dfw.source.kernel.org (Postfix) with ESMTP id 8789961A01; Tue, 7 May 2024 23:11:56 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id F21B8C2BBFC; Tue, 7 May 2024 23:11:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1715123516; bh=qjiSmLpHA1Dv+SZcM5vbpRQi0La7wupBj5UpNueurXE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=WHiKDmEytbjMEs3stArdo8KjgpnnKxV0dmRr7VlG157pZj6dO4rvsGaR0GfztQVnQ y/7njJWhuIF4sDW22wIlMRTMYisW7yqrjBXxrmjytsDUAwME0uNBEEjN6IuDn7pEn4 YyUZe0S90EdAmipBB1AjOXgHZlFJ9Rvck8KLNPhtA9FWJ7XvsypPWyZvAQgQrefu1r EfLeydOxaC/d+HKGUNJ+S0+D5l8w2PwgMyZY0vwtqQlNjEVRvpgkUU7VScrRjgsCpk qK2OFiTHIr/5W7tWtxrOixpASVATVygFGIepMhSmURUeoWFrHUvbGhkH4PFDZJC8S0 0GSizEguVmThg== 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 6.6 35/43] drm/amdkfd: Flush the process wq before creating a kfd_process Date: Tue, 7 May 2024 19:09:56 -0400 Message-ID: <20240507231033.393285-35-sashal@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240507231033.393285-1-sashal@kernel.org> References: <20240507231033.393285-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore X-stable-base: Linux 6.6.30 Content-Transfer-Encoding: 8bit X-BeenThere: amd-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Discussion list for AMD gfx List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: amd-gfx-bounces@lists.freedesktop.org Sender: "amd-gfx" 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 7a1a574106fac..d98e45aec76b4 100644 --- a/drivers/gpu/drm/amd/amdkfd/kfd_process.c +++ b/drivers/gpu/drm/amd/amdkfd/kfd_process.c @@ -828,6 +828,14 @@ struct kfd_process *kfd_create_process(struct task_struct *thread) 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