From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ed1-f70.google.com (mail-ed1-f70.google.com [209.85.208.70]) by kanga.kvack.org (Postfix) with ESMTP id AF9E56B30E3 for ; Fri, 23 Nov 2018 06:03:04 -0500 (EST) Received: by mail-ed1-f70.google.com with SMTP id q8so451815edd.8 for ; Fri, 23 Nov 2018 03:03:04 -0800 (PST) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id t21-v6sor6960561ejx.10.2018.11.23.03.03.03 for (Google Transport Security); Fri, 23 Nov 2018 03:03:03 -0800 (PST) Date: Fri, 23 Nov 2018 12:02:55 +0100 From: Andrea Parri Subject: Re: [PATCH v2] kmemleak: Turn kmemleak_lock to raw spinlock on RT Message-ID: <20181123110226.GA5125@andrea> References: <1542877459-144382-1-git-send-email-zhe.he@windriver.com> <20181123095314.hervxkxtqoixovro@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181123095314.hervxkxtqoixovro@linutronix.de> Sender: owner-linux-mm@kvack.org List-ID: To: Sebastian Andrzej Siewior Cc: zhe.he@windriver.com, catalin.marinas@arm.com, tglx@linutronix.de, rostedt@goodmis.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-rt-users@vger.kernel.org, boqun.feng@gmail.com > is this an RT-only problem? Because mainline should not allow read->read > locking or read->write locking for reader-writer locks. If this only > happens on v4.18 and not on v4.19 then something must have fixed it. Probably misunderstanding, but I'd say that read->read locking is "the norm"...? If you don't use qrwlock, readers are also "recursive", in part., P0 P1 read_lock(l) write_lock(l) read_lock(l) won't block P0 on the second read_lock(). (qrwlock somehow complicate the analysis; IIUC, they are recursive if and only if in_interrupt().). Andrea > > > Sebastian