From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 C6E782066DB for ; Thu, 3 Apr 2025 12:28:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1743683327; cv=none; b=nx3j2TSASvTkb/SJe1/tPrzm/U/jpIrH/j6ZmKOSNTOQo3muGTCeO5nNiat/c63V59LlnY25ArMwSppi5nSe1SuRxCFUQvkY3eQvlJ5PICQ/pe0nnQdU+XWu3SkRs48Ww6BGRxGoehjYVj4nDVMjxARuAdXuZRCq6cAl6KEKi6Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1743683327; c=relaxed/simple; bh=ELUcPUXOUkvzl1zye8wYAOKK9OCpZ0wfFvrzbkp0IBs=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=I5uAot+1BfAxuHNLF3aZMbi5ZBGDCz8Oc5tTBcbxZJIMD0rIt7CHSj6vyfD/dz2Waus51A+cwkwJ3AWphLti6M58lALXTrgxUFzuD1p7bEvNIHjyZkCNqO+x4Auhl1CmYOjmSwUukX67RcyMwzqH7nO5EMLDBwaVkWQuywYRjbc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=LU1TSPi2; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="LU1TSPi2" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1743683324; 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=ELUcPUXOUkvzl1zye8wYAOKK9OCpZ0wfFvrzbkp0IBs=; b=LU1TSPi2aiCTXJKZKY+A4oBirsugk9ElJBfs8pMs4v4PL0Hp4WEeS0WtCUYz+g7VIS1vE9 GDO4IviRfbGJT8/DM88DJk8wGkvr5PEPYLhMKaJG6ZASg1U48PkIlcVVb7pKsEtPeHZyKp JS0StQ+p+9j1YOszSjASZjln6JomZkw= Received: from mx-prod-mc-02.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-3-iuFU7Jo0NumtkN1C3UahXw-1; Thu, 03 Apr 2025 08:28:38 -0400 X-MC-Unique: iuFU7Jo0NumtkN1C3UahXw-1 X-Mimecast-MFC-AGG-ID: iuFU7Jo0NumtkN1C3UahXw_1743683316 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 8D133195608A; Thu, 3 Apr 2025 12:28:36 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.44.32.20]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with SMTP id 0FD921809B6C; Thu, 3 Apr 2025 12:28:32 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Thu, 3 Apr 2025 14:28:01 +0200 (CEST) Date: Thu, 3 Apr 2025 14:27:56 +0200 From: Oleg Nesterov To: Sebastian Sewior 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: <20250403122756.GB16254@redhat.com> 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> <20250403073728.c7kEmd8l@linutronix.de> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250403073728.c7kEmd8l@linutronix.de> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 On 04/03, Sebastian Sewior wrote: > > On 2025-04-02 16:12:46 [+0200], Oleg Nesterov wrote: > > > > > > 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. Well, Andrii has already explained why he decided to abuse seqcount_t, to avoid the explicti barriers in this code... I won't argue. So, just in case, I agree that your suggestion to use raw_write_seqcount_begin/end should obviously fix the problem. Oleg.