linux-kernel - CONFIG_PREEMPT

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-next>] [day] [month] [year] [list]

Date:	Sat, 8 Aug 2009 20:34:03 +0100 (BST)
From:	Hugh Dickins <hugh.dickins@...cali.co.uk>
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
cc:	Ingo Molnar <mingo@...e.hu>,
	Ben Herrenschmidt <benh@...nel.crashing.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: CONFIG_PREEMPT_RCU in next/mmotm

Hi Paul,

Is CONFIG_PREEMPT_RCU=y expected to be working in -next (or mmotm)?

I ask because it appears to break down on PowerPC G5 when I try two
"make -j20" kernel builds in parallel.  The "filp" slab which usually
contains a couple of thousand objects or so, jumps up to a couple of
hundred thousand before the builds complete, and continues rising
from then on - I think that's a sign of RCU in disgrace?
And rebooting hangs thereafter.

And I notice that include/linux/rcupreempt.h currently says:
static inline void synchronize_rcu_expedited(void)
{
	synchronize_rcu();  /* Placeholder for new rcupreempt implementation. */
}
which gives an impression of work in progress?

CONFIG_PREEMPT_TREE=y seems okay on PowerPC; and when I briefly tried
CONFIG_PREEMPT_RCU=y on x86_64, it didn't show above symptoms there.

I did try bisecting yesterday's linux-next git, but that led me to

commit 8ca17c6082feee5841a7b0e91d00e18c3f85f063
Merge: dafcc6e... 7256cf0...
Author: Ingo Molnar <mingo@...e.hu>
Date:   Mon Aug 3 15:50:37 2009 +0200

    Merge branch 'core/rcu' into auto-sched-next

rather than to any particular patch of yours which that merges:
which seemed odd, but I'm not accustomed to bisecting next.

Another odd thing is that mmotm .DATE=2009-07-30-05-01, the last
I tried before Thursday's, showed no such symptoms: yet appears to
contain all the larger RCU changes, just lacking some more recent
on/offline race fixes.  I didn't notice any likely difference
between those mmotm trees down in arch/powerpc either.

My guess is that there's some other issue which is triggering
the RCU disgrace, but that is just a guess.

Config attached.  Any suggestions?

Thanks,
Hugh
--
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/