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Message-ID: <20110801180151.GA26686@albatros> Date: Mon, 1 Aug 2011 22:01:51 +0400 From: Vasiliy Kulikov <segoon@...nwall.com> To: Andrew Morton <akpm@...ux-foundation.org> Cc: Ingo Molnar <mingo@...e.hu>, kernel-hardening@...ts.openwall.com, "Paul E. McKenney" <paul.mckenney@...aro.org>, Manuel Lauss <manuel.lauss@...glemail.com>, linux-kernel@...r.kernel.org, Richard Weinberger <richard@....at>, torvalds@...ux-foundation.org, Marc Zyngier <maz@...terjones.org> Subject: initcall dependency problem (ns vs. threads) Hi, There were reported problems with recent shm changes, by Manuel Lauss (on MIPS), Richard Weinberger (on UML), and Marc Zyngier (on ARM). https://lkml.org/lkml/2011/8/1/149 https://lkml.org/lkml/2011/8/1/162 https://lkml.org/lkml/2011/8/1/210 The problem became visible on this patch: commit 5774ed014f02120db9a6945a1ecebeb97c2acccb Author: Vasiliy Kulikov <segoon@...nwall.com> Date: Fri Jul 29 03:55:31 2011 +0400 shm: handle separate PID namespaces case It started to use &shm_ids(ns).rw_mutex, which is not initialized yet. Init IPC namespace is initialized as initcall() and some threads are created as early_initcall(). I threat it is a dependency bug in the core kernel - kernel threads should be able to use any namespace information, but currently there is a race between namespace initialization code (which is initcall) and kernel threads (which are early_initcall). I don't feel enough experienced in init code dependencies, so I report it to you. static int __init kernel_init(void * unused) { ... do_pre_smp_initcalls(); << threads start here ... do_basic_setup(); static void __init do_basic_setup(void) { cpuset_init_smp(); usermodehelper_init(); init_tmpfs(); driver_init(); init_irq_proc(); do_ctors(); do_initcalls(); << namespace init here } Thanks, -- Vasiliy
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