From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (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 D79E1241139 for ; Thu, 3 Apr 2025 07:37:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.142.43.55 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1743665859; cv=none; b=lWWH4N/LgnX+O1FqoT9OHxrZGAed+3fVZuWarFQJkLQWBPzycRGuF3JdMAtKUNpK1pac59NymG+OJa63FGUBuzCrddDAp+3AXYu7sLTy4QTWcEw0NohsBzZwAXqECLm19zBV9xwCnbBP1x2Osphd4alsbX8JLyBqAANnSCYSH5M= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1743665859; c=relaxed/simple; bh=0zMH1MgRjq2b3gl7q2kzt7wbggaTuK8vve7tmy3kHXg=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=YfX22KOhG6C2IIn379RvK6JCCveD9FRH3y+Zr5GuXIFdYsubGpPLOoLGgCXLxw9WqymNfOSh8g0N5qYuGPljim448ATTqYXRSvMC3fuyBYB68Vhn/nQBv6ewpWwUh4fZ+B/NpjIXh6jzlvP6X3LhGaMvtIsaU9Qfkz6vDGul1hs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de; spf=pass smtp.mailfrom=linutronix.de; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=j6HpObcH; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=G3bD46Cb; arc=none smtp.client-ip=193.142.43.55 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="j6HpObcH"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="G3bD46Cb" Date: Thu, 3 Apr 2025 09:37:28 +0200 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1743665849; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=y6JbZyxvgeOJnaS61yeYd4hCsKtS7hwmtF1doeYIPX4=; b=j6HpObcHxzEJcf5kwuxqshXhgdN/ypjEQ0zPcYAIAeSX+P8+IEiEF5ULcCZriEPILK2W+j gxRfDIlI6RN3n9Xj3WCtFW3e5Z11HR/LBqexcfVYJ15/mgwGUzURHc+nZQiTPH85ldMo3z 7dRiaQLPb4MVmSpT2HQJ20co1Mmm7rpzaMPVM2P3gL9fR6ELvQCTaU61q8s4wagnbMHT1w lTt3fVcm2Xabmo7ZN/QbinQ73gVtf+I/fV4pIHbvb11jR/JWZ26bZbr7amcCaRglZg3YcU 7vZYxIl2nDvtvoOE8zzFEAd6qBJcmRSg3KBkyco61uv3eTVtfw7q9Mg397J87A== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1743665849; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=y6JbZyxvgeOJnaS61yeYd4hCsKtS7hwmtF1doeYIPX4=; b=G3bD46CbTCyzH9za0iGkt6LLvPPvtBBy3mlyMkjZPtOxenFhdEusCAdIU36LmsVA0WrS/i uPT2Un3/bgyTbYCw== From: Sebastian Sewior To: Oleg Nesterov Cc: Andrii Nakryiko , Steven Rostedt , Peter Ziljstra , Alexei Starovoitov , Andrii Nakryiko , bpf , Jiri Olsa , Masami Hiramatsu Subject: Re: uprobe splat in PREEMP_RT Message-ID: <20250403073728.c7kEmd8l@linutronix.de> References: <20250401172225.06b01b22@gandalf.local.home> <20250402103326.GD22091@redhat.com> <20250402105746.FMPvRBwL@linutronix.de> <20250402112308.GF22091@redhat.com> <20250402121315.UdZVK1JE@linutronix.de> <20250402121850.GI22091@redhat.com> <20250402122447.B3XIrQnG@linutronix.de> <20250402141245.GK22091@redhat.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20250402141245.GK22091@redhat.com> On 2025-04-02 16:12:46 [+0200], Oleg Nesterov wrote: > On 04/02, Sebastian Sewior wrote: > > > > On 2025-04-02 14:18:51 [+0200], Oleg Nesterov wrote: > > > On 04/02, Sebastian Sewior wrote: > > > > I need to tell mutt to replace my name in case it is misspelled. > > Hmm... have I misspelled your name somewhere? > > If yes - my apologies. Don't worry. You didn't start it, it is just I noticed it. > > > > The preempted ri_timer() could stall a read_seqcount_begin(). > > > > > > Again, nobody use read_seqcount_begin(utask->ri_seqcount). > > > > > > free_ret_instance() uses raw_seqcount_try_begin(utask->ri_seqcount), > > > which, since ri_seqcount is seqcount_t, is just smp_load_acquire(). > > > This can't stall. > > > > Yes. This would work for here just to skip the check because of all > > details that are hard to express. Therefore I suggested to use > > raw_write_seqcount_begin() instead of write_seqcount_begin() in > > 20250402122158.j_8VoHQ-@linutronix.de. Would that work? > > If this can work, then let me repeat: why can't we turn ->ri_seqcount > into a boolean? I just stumbled here due to the warning. Now that you ask the question, it is used a bool in the current construct. So yes, I also don't see why. > Oleg. Sebastian