linux-kernel - Re: suspicious RCU usage warnings in 3.3.0

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]

Date:	Fri, 13 Apr 2012 14:55:12 +0300 (EEST)
From:	mroos@...ux.ee
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
cc:	David Miller <davem@...emloft.net>, shemminger@...tta.com,
	Linux Kernel list <linux-kernel@...r.kernel.org>,
	netdev@...r.kernel.org
Subject: Re: suspicious RCU usage warnings in 3.3.0

> sparc64: Eliminate obsolete __handle_softirq() function
> 
> The invocation of softirq is now handled by irq_exit(), so there is no
> need for sparc64 to invoke it on the trap-return path.  In fact, doing so
> is a bug because if the trap occurred in the idle loop, this invocation
> can result in lockdep-RCU failures.  The problem is that RCU ignores idle
> CPUs, and the sparc64 trap-return path to the softirq handlers fails to
> tell RCU that the CPU must be considered non-idle while those handlers
> are executing.  This means that RCU is ignoring any RCU read-side critical
> sections in those handlers, which in turn means that RCU-protected data
> can be yanked out from under those read-side critical sections.
> 
> The shiny new lockdep-RCU ability to detect RCU read-side critical sections
> that RCU is ignoring located this problem.
> 
> The fix is straightforward: Make sparc64 stop manually invoking the
> softirq handlers.
> 
> Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>

It works for me on Sun Fire V100 - no more RCU warnings under ping 
flood.

Tested-by: Meelis Roos <mroos@...ux.ee>

-- 
Meelis Roos (mroos@...ux.ee)
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/