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 A30BA232792 for ; Wed, 2 Apr 2025 12:13:13 +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=1743595995; cv=none; b=JDBf8zXKdnONje6o8mso+AxZf/zDeeQJ+YLM4+c+camWuLGtcIsxLhhGwLjdiLzFv/l77yHQuIdBI5v/mOG2ZySbLRIEmkn9JeJinAiQNza6yBAD+UWVSZOVnrNvknb/vA3d8aNDYYaq8PYszDx3/OHpzZ5GcIrSQG/8r6hjv4c= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1743595995; c=relaxed/simple; bh=m7J6hgaWEfWJ/5Iiun4oGp+y3lQJE65+e0/JQTHCo88=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Soshktdna6OECB47cd8J/daeeWruS24W+8aGsOMK5LciUWaLdcd8/gUJT1VJHlMXesthCLnltkqvOlThUxcbyYolOccvcOkWxmQofAqeaomN/pwGjMZgeeeYP5lqx/M0jrF2895+DjYdTbp0FO17GRKP8G3lsgl66v5wiHrqJKQ= 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=OqS6DB5Q; 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="OqS6DB5Q" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1743595992; 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=m7J6hgaWEfWJ/5Iiun4oGp+y3lQJE65+e0/JQTHCo88=; b=OqS6DB5QGuuZP+fx5qbJ/HeB9H6X7fmiyA/3lHwCmCJqvVFx9Zq1cIN+OkXZDWJO7ABo2D W64Tfv2SUMMKE1jX8JTl4aCwwK8Oqik75k+gbsrPSV84A5/vzZy1Qbr37oWvmGPlLEnFn7 gg3CWioP6udqAQJVemgLORYw4LPNYoU= Received: from mx-prod-mc-05.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-395-RZKhpmmsPC-6LXpEKkbNoA-1; Wed, 02 Apr 2025 08:13:09 -0400 X-MC-Unique: RZKhpmmsPC-6LXpEKkbNoA-1 X-Mimecast-MFC-AGG-ID: RZKhpmmsPC-6LXpEKkbNoA_1743595987 Received: from mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.40]) (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-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 96A1B195608F; Wed, 2 Apr 2025 12:13:07 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.44.34.147]) by mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with SMTP id 7EDE919560AD; Wed, 2 Apr 2025 12:13:04 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Wed, 2 Apr 2025 14:12:32 +0200 (CEST) Date: Wed, 2 Apr 2025 14:12:28 +0200 From: Oleg Nesterov To: Sebastian Sewior Cc: Alexei Starovoitov , Peter Ziljstra , Andrii Nakryiko , bpf , Steven Rostedt , Jiri Olsa , Masami Hiramatsu Subject: Re: uprobe splat in PREEMP_RT Message-ID: <20250402121228.GH22091@redhat.com> References: <20250402091044.GB22091@redhat.com> <20250402105444.tW8UU7vO@linutronix.de> <20250402112007.GE22091@redhat.com> <20250402113142.GG22091@redhat.com> <20250402120649._gQHEtYM@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: <20250402120649._gQHEtYM@linutronix.de> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 3.0 on 10.30.177.40 On 04/02, Sebastian Sewior wrote: > > On 2025-04-02 13:31:43 [+0200], Oleg Nesterov wrote: > > > > IOW. > > > > I understand that seqcount_t is not RT-friendly, but why exactly do > > you think the patch above can make the things worse? > > We wouldn't notice such a case. Sebastian, could you spell please? What case we wouldn't notice? With this patch write_seqcount_begin(seqcount_t) will notice that seqprop_preemptible() is true and do preempt_disable() itself. Oleg.