From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) (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 8FEAB4A3F0D; Fri, 4 Sep 2026 13:47:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=216.40.44.15 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788529665; cv=none; b=J4afCi4Z1BeU2sK8037On2lhKB+BRvZd/iNUILH9/JTPJGyxb2DWvkWH7c8hRVEa1lOAnWTtcCEKlvuYcrwM19C8AGJudBILtjEiYQAi9DgXmtLPf/7Q/FwlLRfrhvSHPgJCRYlMqf97O2xnPmDgVgZKuWqY5KP5om1izOesRJs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788529665; c=relaxed/simple; bh=3QqozabmMHkHUpENbmDig1ETzOhnj3lQ3G3dAmT73V8=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=b0le2GfdqsdjrnakmewarMFiiA2YZxgSY4expxcFOP5A+/7WFxfAluDavKgBM5RNBpI4EvCAxuHnHPGEIVDLb6vdeo+HvuPtUZ/M7dzpjfCJmnm5o1p53Xii5jYBpNCf8JPyu8lnJSS9+gHtPbmRpoMXIeKa5pSVLCRYzpYeXYw= 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; dkim=pass (1024-bit key) header.d=goodmis.org header.i=@goodmis.org header.b=qZd82czN; arc=none smtp.client-ip=216.40.44.15 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 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=goodmis.org header.i=@goodmis.org header.b="qZd82czN" Received: from omf16.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay09.hostedemail.com (Postfix) with ESMTP id 9A11A81432; Fri, 4 Sep 2026 13:46:33 +0000 (UTC) Received: from [HIDDEN] (Authenticated sender: rostedt@goodmis.org) by omf16.hostedemail.com (Postfix) with ESMTPA id BAB8620019; Fri, 4 Sep 2026 13:46:28 +0000 (UTC) Date: Fri, 4 Sep 2026 09:47:33 -0400 From: Steven Rostedt To: Ran Hongyun Cc: , , , , , , , , , , , , , , , , , , , , , , , Subject: Re: [QUESTION] Are these issues PREEMPT_RT-specific? Message-ID: <20260904094733.538d2af6@gandalf.local.home> In-Reply-To: <20260904081149.3000727-1-ranhongyun1@huawei.com> References: <20260904081149.3000727-1-ranhongyun1@huawei.com> X-Mailer: Claws Mail 3.20.0git84 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-Stat-Signature: psh8ie81d61q8baqnffyuct988cftytm X-Rspamd-Server: rspamout02 X-Rspamd-Queue-Id: BAB8620019 X-Session-Marker: 726F737465647440676F6F646D69732E6F7267 X-Session-ID: U2FsdGVkX19TT+Uqsvs68jLi/HGrQRy0ZkJtDf+Yw7A= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=goodmis.org; h=date:from:to:cc:subject:message-id:in-reply-to:references:mime-version:content-type:content-transfer-encoding; s=dkim1; bh=3QqozabmMHkHUpENbmDig1ETzOhnj3lQ3G3dAmT73V8=; b=qZd82czN5zoTGFHIggmhPCvwpL3n8aR7RjkZ9o1RXnRkWHkwxhx+raYkfoqpNaQ5uJxRob83n61gaHyGfzQhhsXqgkPCYdZJe6yniHpvfPimWBMWvVDRAw9erkORHDUJOPIB736vPU6E3JxroHiuIkq/SBXHKmc2YCqy/vRstxU= X-HE-Tag: 1788529588-590148 X-HE-Meta: U2FsdGVkX1+vA/2/aWD7umZnnOVnwj+AOUZGPU6in8BExdihItVQ54rOyPf683PlAhickS/DeDAzLjWCsXjVa3msdvYh00OIuCmMUP1/dFmMHqG3mzuWwvV6Oi2gSXVyI8Sj3L9ixgLSx2LYvAFgiAMplhjtWnVEnpy6AP0lDmA4ZJjtG+KQq+FDl9XxMvPvpTz2MH7skVNTBlXX3rOPsMTmf6NIgGr80Gayq3I8hFqoXI8xoW+CSLBPB1b+pYf2t8DHZ7w0DwYQrmpMlm33/8HS5Ce8OAXbPuORtwp4ol9veT5wBM099i+S4zzUUZTRg/de4GFfKz2eJO+igNMbh1Gc+XEdsLZ8 On Fri, 4 Sep 2026 16:11:41 +0800 Ran Hongyun wrote: > 1.Priority inversion =E2=80=93 On PREEMPT_RT, rwlock_t readers lack prior= ity > inheritance (PI), so a low-priority reader holding the lock can be > preempted by a medium-priority task, blocking a high-priority writer > indefinitely. Priority inheritance to boost readers from a writer is an exponentially difficult problem to solve. PI is already hard enough, but multiple readers is exponentially more difficult (we tried). The solution is to make sure you do not have any RT critical tasks taking rw writer locks. This is something that the Runtime Verifier (RV) can help make sure you never hit this situation. -- Steve