From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) (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 5145635CBC5; Fri, 14 Nov 2025 15:46:25 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=216.40.44.11 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763135187; cv=none; b=MPljxUQFSjZ/K6+vzHhoW/q6ZbyHrEjUrzwK7FMX0i6bKj3S4iMOMWGKePH9N9uNRMpS3igat3MtF+b1181AUjSUoaMNwmBwNZ3WP3r/9ZUZMieo0WAB9OeDcXGMj1gYbLCcbEOUJYcC9U4QLZmqxfWqFefO3miM337Vu0I1J90= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763135187; c=relaxed/simple; bh=laLfkcfKkv6qg5lFpKg6jiDdx3PoXhOBfQDJd538wQY=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=az3CURreFG/24QLE0iQaD3LwemwTgJu2kh9Ug6m28SGn6CI/RW533VpxWPIrx+a2qxzT0wwJl2cYoT+aU9ek24pL4MqfkMlJKEalI1IPZZcr0gzPAKFB2Gk7O8UM5FdsePra/2U6ywdWusSBWdODSRnhM/F58vuvDY3RsRHcn9E= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=goodmis.org; spf=pass smtp.mailfrom=goodmis.org; arc=none smtp.client-ip=216.40.44.11 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=goodmis.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=goodmis.org Received: from omf18.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id 492A41603A6; Fri, 14 Nov 2025 15:46:17 +0000 (UTC) Received: from [HIDDEN] (Authenticated sender: rostedt@goodmis.org) by omf18.hostedemail.com (Postfix) with ESMTPA id 35D1334; Fri, 14 Nov 2025 15:46:15 +0000 (UTC) Date: Fri, 14 Nov 2025 10:46:33 -0500 From: Steven Rostedt To: Sebastian Andrzej Siewior Cc: Stephen Rothwell , "Paul E. McKenney" , Frederic Weisbecker , Neeraj Upadhyay , Boqun Feng , Uladzislau Rezki , Masami Hiramatsu , Linux Kernel Mailing List , Linux Next Mailing List Subject: Re: linux-next: manual merge of the rcu tree with the ftrace tree Message-ID: <20251114104633.0721bdbe@gandalf.local.home> In-Reply-To: <20251114133532.mmdi2dca@linutronix.de> References: <20251114135226.64831207@canb.auug.org.au> <20251114074255.3e535084@gandalf.local.home> <20251114133532.mmdi2dca@linutronix.de> X-Mailer: Claws Mail 3.20.0git84 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Stat-Signature: 71d6jbz4b71exe1jxfhdtiq5hk1d4beb X-Rspamd-Server: rspamout07 X-Rspamd-Queue-Id: 35D1334 X-Session-Marker: 726F737465647440676F6F646D69732E6F7267 X-Session-ID: U2FsdGVkX1+WrHBcHWCBxqK4sDwnLzRx4nfYp1IllHY= X-HE-Tag: 1763135175-639753 X-HE-Meta: U2FsdGVkX1+e0Vuwmnc+B3ehOmag63D2pqwiZycDiPFGlqywRInc/Uvq2CgYGyQjVJtlHqtQ4PHVbPUaFYd2rWLXCim71oGwblzgPX8Jm+TGuXHdYc/N6edOzk1ZAy4UdxziHViDAJcbt0w/hIUaxxDD3ihjRlPJ2niF7W9f3roGv5IIlgarJqPAVgqzBC3CKlBH7ft+iO9EK9VlVhcK78o8hBjCoHsOeVhWLmEX4uTYOQCzbqXQl5gzlBhaJPlVJjh1VC6Oq5qYzuWO4AG5Y4tZXK/vb1wBRObip/C20c93dckvc5cdBkyzY0sj9Dtl On Fri, 14 Nov 2025 14:35:32 +0100 Sebastian Andrzej Siewior wrote: > On 2025-11-14 07:42:55 [-0500], Steven Rostedt wrote: > > > diff --cc kernel/trace/trace_syscalls.c > > > index e96d0063cbcf,3f699b198c56..000000000000 > > > --- a/kernel/trace/trace_syscalls.c > > > +++ b/kernel/trace/trace_syscalls.c > > > @@@ -878,6 -322,8 +890,7 @@@ static void ftrace_syscall_enter(void * > > > * buffer and per-cpu data require preemption to be disabled. > > > */ > > > might_fault(); > > > + preempt_rt_guard(); > > > - guard(preempt_notrace)(); > > > > My code made it so that preemption is not needed here but is moved later > > down for the logic that does the reading of user space data. > > > > Note, it must have preemption disabled for all configs (including RT). > > Otherwise, the data it has can get corrupted. > > > > Paul, can you change it so that you *do not* touch this file? > > Where is preempt_rt_guard() from? Ah, it's from the patch I submitted that has this: +/* + * When PREEMPT_RT is enabled, it disables migration instead + * of preemption. The pseudo syscall trace events need to match + * so that the counter logic recorded into he ring buffer by + * trace_event_buffer_reserve() still matches what it expects. + */ +#ifdef CONFIG_PREEMPT_RT +# define preempt_rt_guard() guard(migrate)() +#else +# define preempt_rt_guard() +#endif + I must be getting old, as I forgot I wrote this :-p I only saw the update from Stephen and thought it was disabling preemption. It doesn't disable preemption, but is here to keep the latency preempt_count counting the same in both PREEMPT_RT and non PREEMPT_RT. You know, the stuff that shows up in the trace: "d..4." Paul, never mind, this code will not affect the code I added. -- Steve