linux-kernel - Re: possible circular locking dependency detected [was: linux-next: Tree for Aug 22]

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20170823055517.GB728@jagdpanzerIV.localdomain>
Date:   Wed, 23 Aug 2017 14:55:17 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     Boqun Feng <boqun.feng@...il.com>
Cc:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Byungchul Park <byungchul.park@....com>,
        Bart Van Assche <Bart.VanAssche@....com>,
        peterz@...radead.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        "martin.petersen@...cle.com" <martin.petersen@...cle.com>,
        "axboe@...nel.dk" <axboe@...nel.dk>,
        "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        "sfr@...b.auug.org.au" <sfr@...b.auug.org.au>,
        "linux-next@...r.kernel.org" <linux-next@...r.kernel.org>,
        kernel-team@....com
Subject: Re: possible circular locking dependency detected [was: linux-next:
 Tree for Aug 22]

On (08/23/17 13:35), Boqun Feng wrote:
> > KERN_CONT and "\n" should not be together. "\n" flushes the cont
> > buffer immediately.
> > 
> 
> Hmm.. Not quite familiar with printk() stuffs, but I could see several
> usages of printk(KERN_CONT "...\n") in kernel.
> 
> Did a bit research myself, and I now think the inappropriate use is to
> use a KERN_CONT printk *after* another printk ending with a "\n".

ah... I didn't check __print_lock_name(): it leaves unflushed cont buffer
upon the return. sorry, your code is correct.

	-ss

> > >  		printk("\n *** DEADLOCK ***\n\n");
> > > +	} else if (cross_lock(src->instance)) {
> > > +		printk(" Possible unsafe locking scenario by crosslock:\n\n");
> > > +		printk("       CPU0                    CPU1\n");
> > > +		printk("       ----                    ----\n");
> > > +		printk("  lock(");
> > > +		__print_lock_name(target);
> > > +		printk(KERN_CONT ");\n");
> > > +		printk("  lock(");
> > > +		__print_lock_name(source);
> > > +		printk(KERN_CONT ");\n");
> > > +		printk("                               lock(");
> > > +		__print_lock_name(parent == source ? target : parent);
> > > +		printk(KERN_CONT ");\n");
> > > +		printk("                               unlock(");
> > > +		__print_lock_name(source);
> > > +		printk(KERN_CONT ");\n");
> > > +		printk("\n *** DEADLOCK ***\n\n");
> > >  	} else {
> > >  		printk(" Possible unsafe locking scenario:\n\n");
> > >  		printk("       CPU0                    CPU1\n");
> > > -- 
> > > 2.14.1
> > >