Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752608AbdHKDop (ORCPT ); Thu, 10 Aug 2017 23:44:45 -0400 Received: from LGEAMRELO11.lge.com ([156.147.23.51]:57854 "EHLO lgeamrelo11.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752262AbdHKDoo (ORCPT ); Thu, 10 Aug 2017 23:44:44 -0400 X-Original-SENDERIP: 156.147.1.151 X-Original-MAILFROM: byungchul.park@lge.com X-Original-SENDERIP: 10.177.222.33 X-Original-MAILFROM: byungchul.park@lge.com Date: Fri, 11 Aug 2017 12:43:28 +0900 From: Byungchul Park To: Boqun Feng Cc: peterz@infradead.org, mingo@kernel.org, tglx@linutronix.de, walken@google.com, kirill@shutemov.name, linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, willy@infradead.org, npiggin@gmail.com, kernel-team@lge.com Subject: Re: [PATCH v8 06/14] lockdep: Detect and handle hist_lock ring buffer overwrite Message-ID: <20170811034328.GH20323@X58A-UD3R> References: <1502089981-21272-1-git-send-email-byungchul.park@lge.com> <1502089981-21272-7-git-send-email-byungchul.park@lge.com> <20170810115922.kegrfeg6xz7mgpj4@tardis> <016b01d311d1$d02acfa0$70806ee0$@lge.com> <20170810125133.2poixhni4d5aqkpy@tardis> <20170810131737.skdyy4qcxlikbyeh@tardis> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170810131737.skdyy4qcxlikbyeh@tardis> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3602 Lines: 105 On Thu, Aug 10, 2017 at 09:17:37PM +0800, Boqun Feng wrote: > > > > > @@ -4826,6 +4851,7 @@ static inline int depend_after(struct held_lock > > > > *hlock) > > > > > * Check if the xhlock is valid, which would be false if, > > > > > * > > > > > * 1. Has not used after initializaion yet. > > > > > + * 2. Got invalidated. > > > > > * > > > > > * Remind hist_lock is implemented as a ring buffer. > > > > > */ > > > > > @@ -4857,6 +4883,7 @@ static void add_xhlock(struct held_lock *hlock) > > > > > > > > > > /* Initialize hist_lock's members */ > > > > > xhlock->hlock = *hlock; > > > > > + xhlock->hist_id = current->hist_id++; > > > > Besides, is this code correct? Does this just make xhlock->hist_id > > one-less-than the curr->hist_id, which cause the invalidation every time > > you do ring buffer unwinding? > > > > Regards, > > Boqun > > > > So basically, I'm suggesting do this on top of your patch, there is also > a fix in commit_xhlocks(), which I think you should swap the parameters > in before(...), no matter using task_struct::hist_id or using > task_struct::xhlock_idx as the timestamp. > > Hope this could make my point more clear, and if I do miss something, > please point it out, thanks ;-) Sorry for mis-understanding. I like your patch. I think it works. Additionally.. See below.. > diff --git a/include/linux/sched.h b/include/linux/sched.h > index 074872f016f8..886ba79bfc38 100644 > --- a/include/linux/sched.h > +++ b/include/linux/sched.h > @@ -854,9 +854,6 @@ struct task_struct { > unsigned int xhlock_idx; > /* For restoring at history boundaries */ > unsigned int xhlock_idx_hist[XHLOCK_NR]; > - unsigned int hist_id; > - /* For overwrite check at each context exit */ > - unsigned int hist_id_save[XHLOCK_NR]; > #endif > > #ifdef CONFIG_UBSAN > diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c > index 699fbeab1920..04c6c8d68e18 100644 > --- a/kernel/locking/lockdep.c > +++ b/kernel/locking/lockdep.c > @@ -4752,10 +4752,8 @@ void crossrelease_hist_start(enum xhlock_context_t c) > { > struct task_struct *cur = current; > > - if (cur->xhlocks) { > + if (cur->xhlocks) > cur->xhlock_idx_hist[c] = cur->xhlock_idx; > - cur->hist_id_save[c] = cur->hist_id; > - } > } > > void crossrelease_hist_end(enum xhlock_context_t c) > @@ -4769,7 +4767,7 @@ void crossrelease_hist_end(enum xhlock_context_t c) > cur->xhlock_idx = idx; > > /* Check if the ring was overwritten. */ > - if (h->hist_id != cur->hist_id_save[c]) > + if (h->hist_id != idx) > invalidate_xhlock(h); > } > } > @@ -4849,7 +4847,7 @@ static void add_xhlock(struct held_lock *hlock) > > /* Initialize hist_lock's members */ > xhlock->hlock = *hlock; > - xhlock->hist_id = current->hist_id++; > + xhlock->hist_id = idx; > > xhlock->trace.nr_entries = 0; > xhlock->trace.max_entries = MAX_XHLOCK_TRACE_ENTRIES; > @@ -5005,7 +5003,7 @@ static int commit_xhlock(struct cross_lock *xlock, struct hist_lock *xhlock) > static void commit_xhlocks(struct cross_lock *xlock) > { > unsigned int cur = current->xhlock_idx; > - unsigned int prev_hist_id = xhlock(cur).hist_id; > + unsigned int prev_hist_id = cur + 1; I should have named it another. Could you suggest a better one? > unsigned int i; > > if (!graph_lock()) > @@ -5030,7 +5028,7 @@ static void commit_xhlocks(struct cross_lock *xlock) > * hist_id than the following one, which is impossible > * otherwise. Or we need to modify the comment so that the word 'prev' does not make readers confused. It was my mistake. Thanks, Byungchul