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[PATCH] ppc32: fix destroy_context() race condition

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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 <gautran@mrv.com>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Guillaume Autran
2005-07-13 01:10:45 -07:00
committed by Linus Torvalds
parent 88bd5121d6
commit ddca3b80ce
1 changed files with 2 additions and 0 deletions
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2
include/asm-ppc/mmu_context.h
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@ -149,6 +149,7 @@ static inline void get_mmu_context(struct mm_struct *mm)
*/ */
static inline void destroy_context(struct mm_struct *mm) static inline void destroy_context(struct mm_struct *mm)
{ {
preempt_disable();
if (mm->context != NO_CONTEXT) { if (mm->context != NO_CONTEXT) {
clear_bit(mm->context, context_map); clear_bit(mm->context, context_map);
mm->context = NO_CONTEXT; mm->context = NO_CONTEXT;
@ -156,6 +157,7 @@ static inline void destroy_context(struct mm_struct *mm)
atomic_inc(&nr_free_contexts); atomic_inc(&nr_free_contexts);
#endif #endif
} }
preempt_enable();
} }
static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next, static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,