From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mailman.xyplex.com (mailman.xyplex.com [140.179.176.116]) by ozlabs.org (Postfix) with ESMTP id 8A31667B9A for ; Wed, 13 Jul 2005 00:22:29 +1000 (EST) Message-ID: <42D3D277.106@mrv.com> Date: Tue, 12 Jul 2005 10:23:51 -0400 From: Guillaume Autran MIME-Version: 1.0 To: akpm@osdl.org Content-Type: text/plain; charset=us-ascii; format=flowed Cc: linuxppc-embedded@ozlabs.org Subject: [PATCH] ppc32: fix destroy_context() race condition List-Id: Linux on Embedded PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Fix for a race condition when a task gets preempted by another task while executing the destroy_context(...) in a FEW_CONTEXTS environment. mm->context == NO_CONTEXT but the context_map may indicate all contexts are in use. The solution to this problem is to disable kernel preemption while destroying a MMU context. Signed-off-by: Guillaume Autran --- diff -Nru a/include/asm-ppc/mmu_context.h b/include/asm-ppc/mmu_context.h --- a/include/asm-ppc/mmu_context.h 2005-06-17 15:48:29.000000000 -0400 +++ b/include/asm-ppc/mmu_context.h 2005-07-05 08:58:46.000000000 -0400 @@ -149,6 +149,7 @@ */ static inline void destroy_context(struct mm_struct *mm) { + preempt_disable(); if (mm->context != NO_CONTEXT) { clear_bit(mm->context, context_map); mm->context = NO_CONTEXT; @@ -156,6 +157,7 @@ atomic_inc(&nr_free_contexts); #endif } + preempt_enable(); } static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,