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author | Benjamin Herrenschmidt <benh@kernel.crashing.org> | 2009-05-19 16:56:42 +0000 |
---|---|---|
committer | Benjamin Herrenschmidt <benh@kernel.crashing.org> | 2009-06-09 16:42:21 +1000 |
commit | 3035c8634f0538a0c6946e3191bb6c9284b63798 (patch) | |
tree | 68f81301d2ced6492957c8320a631ad96518bd53 /arch/powerpc | |
parent | ec097c84dff17511f2693e6ef6c3064dfbf0a3af (diff) | |
download | op-kernel-dev-3035c8634f0538a0c6946e3191bb6c9284b63798.zip op-kernel-dev-3035c8634f0538a0c6946e3191bb6c9284b63798.tar.gz |
powerpc/mm: Fix some SMP issues with MMU context handling
This patch fixes a couple of issues that can happen as a result
of steal_context() dropping the context_lock when all possible
PIDs are ineligible for stealing (hopefully an extremely hard to
hit occurence).
This case exposes the possibility of a stale context_mm[] entry
to be seen since destroy_context() doesn't clear it and the free
map isn't re-tested. It also means steal_context() will not notice
a context freed while the lock was help, thus possibly trying to
steal a context when a free one was available.
This fixes it by always returning to the caller from steal_context
when it dropped the lock with a return value that causes the
caller to re-samble the number of free contexts, along with
properly clearing the context_mm[] array for destroyed contexts.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Diffstat (limited to 'arch/powerpc')
-rw-r--r-- | arch/powerpc/mm/mmu_context_nohash.c | 12 |
1 files changed, 8 insertions, 4 deletions
diff --git a/arch/powerpc/mm/mmu_context_nohash.c b/arch/powerpc/mm/mmu_context_nohash.c index 030d000..c428587 100644 --- a/arch/powerpc/mm/mmu_context_nohash.c +++ b/arch/powerpc/mm/mmu_context_nohash.c @@ -73,7 +73,6 @@ static unsigned int steal_context_smp(unsigned int id) struct mm_struct *mm; unsigned int cpu, max; - again: max = last_context - first_context; /* Attempt to free next_context first and then loop until we manage */ @@ -108,7 +107,9 @@ static unsigned int steal_context_smp(unsigned int id) spin_unlock(&context_lock); cpu_relax(); spin_lock(&context_lock); - goto again; + + /* This will cause the caller to try again */ + return MMU_NO_CONTEXT; } #endif /* CONFIG_SMP */ @@ -194,6 +195,8 @@ void switch_mmu_context(struct mm_struct *prev, struct mm_struct *next) WARN_ON(prev->context.active < 1); prev->context.active--; } + + again: #endif /* CONFIG_SMP */ /* If we already have a valid assigned context, skip all that */ @@ -212,7 +215,8 @@ void switch_mmu_context(struct mm_struct *prev, struct mm_struct *next) #ifdef CONFIG_SMP if (num_online_cpus() > 1) { id = steal_context_smp(id); - goto stolen; + if (id == MMU_NO_CONTEXT) + goto again; } #endif /* CONFIG_SMP */ id = steal_context_up(id); @@ -286,8 +290,8 @@ void destroy_context(struct mm_struct *mm) mm->context.id = MMU_NO_CONTEXT; #ifdef DEBUG_MAP_CONSISTENCY mm->context.active = 0; - context_mm[id] = NULL; #endif + context_mm[id] = NULL; nr_free_contexts++; } spin_unlock(&context_lock); |