2008-10-17 05:43:50

by Iwo Mergler

Subject: Fix for genalloc locking

Hi,

I hit a little problem while using genalloc with a mix
of interrupt/non-interrupt context. I believe the correct
fix is to replace the locking calls with the _irqsave/_irqrestore
variants. Patch follows.

Is this correct?

BTW, is there any documentation on the Lockdep warnings?
What exactly is the meaning of {--+.} in

(&pool->lock){--+.}, at: [<c0125d1c>] gen_pool_free+0x34/0x120


Kind regards,

Iwo

2008-10-17 05:46:37

by Iwo Mergler

Subject: Re: [PATCH] Fix for genalloc locking

Genalloc was using a rwlock without irqsave/irqrestore. This
caused problems when used with a mix of int/non-int calls.
Replaced all locking functions with the irqsave/restore
variants.

Signed-off-by: [email protected]

---
lib/genalloc.c | 21 ++++++++++++---------
1 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/lib/genalloc.c b/lib/genalloc.c
index f6d276d..337f05a 100644
--- a/lib/genalloc.c
+++ b/lib/genalloc.c
@@ -49,6 +49,7 @@ EXPORT_SYMBOL(gen_pool_create);
int gen_pool_add(struct gen_pool *pool, unsigned long addr, size_t size,
int nid)
{
+ unsigned long rwflags;
struct gen_pool_chunk *chunk;
int nbits = size >> pool->min_alloc_order;
int nbytes = sizeof(struct gen_pool_chunk) +
@@ -62,9 +63,9 @@ int gen_pool_add(struct gen_pool *pool, unsigned long addr, size_t size,
chunk->start_addr = addr;
chunk->end_addr = addr + size;

- write_lock(&pool->lock);
+ write_lock_irqsave(&pool->lock, rwflags);
list_add(&chunk->next_chunk, &pool->chunks);
- write_unlock(&pool->lock);
+ write_unlock_irqrestore(&pool->lock, rwflags);

return 0;
}
@@ -83,9 +84,9 @@ void gen_pool_destroy(struct gen_pool *pool)
struct gen_pool_chunk *chunk;
int order = pool->min_alloc_order;
int bit, end_bit;
+ unsigned long rwflags;

-
- write_lock(&pool->lock);
+ write_lock_irqsave(&pool->lock, rwflags);
list_for_each_safe(_chunk, _next_chunk, &pool->chunks) {
chunk = list_entry(_chunk, struct gen_pool_chunk, next_chunk);
list_del(&chunk->next_chunk);
@@ -116,13 +117,14 @@ unsigned long gen_pool_alloc(struct gen_pool *pool, size_t size)
unsigned long addr, flags;
int order = pool->min_alloc_order;
int nbits, bit, start_bit, end_bit;
+ unsigned long rwflags;

if (size == 0)
return 0;

nbits = (size + (1UL << order) - 1) >> order;

- read_lock(&pool->lock);
+ read_lock_irqsave(&pool->lock, rwflags);
list_for_each(_chunk, &pool->chunks) {
chunk = list_entry(_chunk, struct gen_pool_chunk, next_chunk);

@@ -149,12 +151,12 @@ unsigned long gen_pool_alloc(struct gen_pool *pool, size_t size)
while (nbits--)
__set_bit(start_bit++, chunk->bits);
spin_unlock_irqrestore(&chunk->lock, flags);
- read_unlock(&pool->lock);
+ read_unlock_irqrestore(&pool->lock, rwflags);
return addr;
}
spin_unlock_irqrestore(&chunk->lock, flags);
}
- read_unlock(&pool->lock);
+ read_unlock_irqrestore(&pool->lock, rwflags);
return 0;
}
EXPORT_SYMBOL(gen_pool_alloc);
@@ -174,10 +176,11 @@ void gen_pool_free(struct gen_pool *pool, unsigned long addr, size_t size)
unsigned long flags;
int order = pool->min_alloc_order;
int bit, nbits;
+ unsigned long rwflags;

nbits = (size + (1UL << order) - 1) >> order;

- read_lock(&pool->lock);
+ read_lock_irqsave(&pool->lock, rwflags);
list_for_each(_chunk, &pool->chunks) {
chunk = list_entry(_chunk, struct gen_pool_chunk, next_chunk);

@@ -192,6 +195,6 @@ void gen_pool_free(struct gen_pool *pool, unsigned long addr, size_t size)
}
}
BUG_ON(nbits > 0);
- read_unlock(&pool->lock);
+ read_unlock_irqrestore(&pool->lock, rwflags);
}
EXPORT_SYMBOL(gen_pool_free);
--
1.6.0

2008-10-21 15:40:45

by Randy Dunlap

Subject: Re: Fix for genalloc locking

On Fri, 17 Oct 2008 16:43:12 +1000 Iwo Mergler wrote:

> Hi,
>
> I hit a little problem while using genalloc with a mix
> of interrupt/non-interrupt context. I believe the correct
> fix is to replace the locking calls with the _irqsave/_irqrestore
> variants. Patch follows.
>
> Is this correct?
>
> BTW, is there any documentation on the Lockdep warnings?
> What exactly is the meaning of {--+.} in
>
> (&pool->lock){--+.}, at: [<c0125d1c>] gen_pool_free+0x34/0x120

Did you read Documentation/lockdep-design.txt ?

---
~Randy

2008-10-21 22:20:30

by Iwo Mergler

Subject: Re: Fix for genalloc locking

Randy Dunlap wrote:
> On Fri, 17 Oct 2008 16:43:12 +1000 Iwo Mergler wrote:
>> BTW, is there any documentation on the Lockdep warnings?
>> What exactly is the meaning of {--+.} in
>>
>> (&pool->lock){--+.}, at: [<c0125d1c>] gen_pool_free+0x34/0x120
>
> Did you read Documentation/lockdep-design.txt ?
>

No, I didn't. Selective blindness. Thanks for the hint.

Kind regards,

Iwo