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 B56A219FA86; Thu, 6 Jun 2024 14:12:16 +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=1717683136; cv=none; b=WgJu8B22S1zeADqGGSiQAemWFztNmbhKp1zhvBCiungla4IgYy24wCBwA0DoJcdLiKFfdeCg38F7inmRKEgCUInCjdhP1b8oxIz/DqzBa3viUhmhUCUxwoZ48Sy0HitWYsEBha8rwP3LrignMsppqyHUkTYoj2f2ML+5l34pNiw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1717683136; c=relaxed/simple; bh=pci7AEIcsLkks9cTV00/2cdndZ4IeamcVpOBQYYl72E=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=tuodhvy4XHM+LzIrA7Z4GlYAHrub1zl2hDddJnRxhhyqcaFNULgL67tWAJuhTjyEyMr4HsYMi/ZbgM7KHuyZW4oFAvmRBY827PTjCZUNxQmn2hwslFWE1l2unl1Gs/gD/nFBVTjtFsg2gYg9lbKiPWOBWKwY/T8xauN/BOFn5IU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=BW/ayBDa; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="BW/ayBDa" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8957CC2BD10; Thu, 6 Jun 2024 14:12:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1717683136; bh=pci7AEIcsLkks9cTV00/2cdndZ4IeamcVpOBQYYl72E=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=BW/ayBDaysAuz3k+K7VDo0I8o8dxHcDfgISwVNkgNwWi9fL8WIRY0xvBTiuQauK1q L9hb8HLYXSCQtqjwmhVoLAKK58ADQAl6jwFzAaKQWIT8MxQdKH/dkvmfkNtOEbRiy3 VEQOrhex8Is82NGBIK5NrHMnnQiuqY58O5O3vWfs= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Lancelot SIX , Felix Kuehling , Alex Deucher , Sasha Levin Subject: [PATCH 6.6 082/744] drm/amdkfd: Flush the process wq before creating a kfd_process Date: Thu, 6 Jun 2024 15:55:54 +0200 Message-ID: <20240606131735.028857596@linuxfoundation.org> X-Mailer: git-send-email 2.45.2 In-Reply-To: <20240606131732.440653204@linuxfoundation.org> References: <20240606131732.440653204@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ 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