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X-CSE-ConnectionGUID: KCxHAUQOQACD9rmsy0w5fA== X-CSE-MsgGUID: 4hX8C3D+SHSGYsnFdt+1aA== X-IronPort-AV: E=McAfee;i="6800,10657,11527"; a="61819855" X-IronPort-AV: E=Sophos;i="6.17,306,1747724400"; d="scan'208";a="61819855" Received: from orviesa010.jf.intel.com ([10.64.159.150]) by fmvoesa106.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 20 Aug 2025 14:42:10 -0700 X-CSE-ConnectionGUID: 2VlKFs7SSNCRSmao/7vngA== X-CSE-MsgGUID: bJSIUcgoQ7OiY4cTFeVATw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.17,306,1747724400"; d="scan'208";a="167457651" Received: from lstrano-mobl6.amr.corp.intel.com (HELO [10.125.108.83]) ([10.125.108.83]) by orviesa010-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 20 Aug 2025 14:42:10 -0700 Message-ID: <7996ef64-59af-4146-be76-95a8aeccfc7a@intel.com> Date: Wed, 20 Aug 2025 14:42:08 -0700 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] x86/process: fix the misleading comment about PF_USER_WORKERs in copy_thread() To: Oleg Nesterov , Borislav Petkov , Dave Hansen , Ingo Molnar , Peter Zijlstra , Thomas Gleixner Cc: Rick Edgecombe , Mark Brown , x86@kernel.org, linux-kernel@vger.kernel.org References: <20250820164651.GA18799@redhat.com> From: Dave Hansen Content-Language: en-US Autocrypt: addr=dave.hansen@intel.com; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 8/20/25 09:46, Oleg Nesterov wrote: > if (unlikely(args->fn)) { > /* > - * A user space thread, but it doesn't return to > - * ret_after_fork(). > + * A non-PF_KTHREAD thread, but it doesn't return from > + * ret_from_fork(). > + * > + * Either a PF_USER_WORKER kernel thread, in this case > + * arg->fn() must not return. > + * Or a user space task created by user_mode_thread(), in > + * this case arg->fn() can only return after a successful > + * kernel_execve(). > * > * In order to indicate that to tools like gdb, > * we reset the stack and instruction pointers. > * > * It does the same kernel frame setup to return to a kernel > - * function that a kernel thread does. > + * function that a PF_KTHREAD thread does. > */ I'm not sure that comment clarifies things, especially the new paragraph. This does _not_ seem like the place to me to be explaining what the conventions are around arg->fn(). It would be better to put it near the definition or 'kernel_clone_args' or the place the function gets called, but not here.