diff mbox series

[bpf-next,v2,1/7] mm/percpu.c: don't acquire pcpu_lock for pcpu_chunk_addr_search()

Message ID 20231018113343.2446300-2-houtao@huaweicloud.com (mailing list archive)
State Superseded
Delegated to: BPF
Headers show
Series bpf: Fixes for per-cpu kptr | expand

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bpf/vmtest-bpf-next-PR success PR summary
netdev/series_format success Posting correctly formatted
netdev/tree_selection success Clearly marked for bpf-next, async
netdev/fixes_present success Fixes tag not required for -next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 1363 this patch: 1363
netdev/cc_maintainers success CCed 6 of 6 maintainers
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netdev/verify_fixes success No Fixes tag
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netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 13 lines checked
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Commit Message

Hou Tao Oct. 18, 2023, 11:33 a.m. UTC 
From: Hou Tao <houtao1@huawei.com>

There is no need to acquire pcpu_lock for pcpu_chunk_addr_search():
1) both pcpu_first_chunk & pcpu_reserved_chunk must have been
   initialized before the invocation of free_percpu().
2) The dynamically-created chunk must be valid before the per-cpu
   pointers allocated from it are freed.

So acquire pcpu_lock() after the invocation of pcpu_chunk_addr_search().

Signed-off-by: Hou Tao <houtao1@huawei.com>
---
 mm/percpu.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

Comments

Dennis Zhou Oct. 20, 2023, 3:55 a.m. UTC | #1 
On Wed, Oct 18, 2023 at 07:33:37PM +0800, Hou Tao wrote:
> From: Hou Tao <houtao1@huawei.com>
> 
> There is no need to acquire pcpu_lock for pcpu_chunk_addr_search():
> 1) both pcpu_first_chunk & pcpu_reserved_chunk must have been
>    initialized before the invocation of free_percpu().
> 2) The dynamically-created chunk must be valid before the per-cpu
>    pointers allocated from it are freed.
> 
> So acquire pcpu_lock() after the invocation of pcpu_chunk_addr_search().
> 
> Signed-off-by: Hou Tao <houtao1@huawei.com>
> ---
>  mm/percpu.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/mm/percpu.c b/mm/percpu.c
> index 7b40b3963f10..76b9c5e63c56 100644
> --- a/mm/percpu.c
> +++ b/mm/percpu.c
> @@ -2267,12 +2267,10 @@ void free_percpu(void __percpu *ptr)
>  	kmemleak_free_percpu(ptr);
>  
>  	addr = __pcpu_ptr_to_addr(ptr);
> -
> -	spin_lock_irqsave(&pcpu_lock, flags);
> -
>  	chunk = pcpu_chunk_addr_search(addr);
>  	off = addr - chunk->base_addr;
>  
> +	spin_lock_irqsave(&pcpu_lock, flags);
>  	size = pcpu_free_area(chunk, off);
>  
>  	pcpu_memcg_free_hook(chunk, off, size);
> -- 
> 2.29.2
> 

Acked-by: Dennis Zhou <dennis@kernel.org>

Thanks,
Dennis
diff mbox series

Patch

diff --git a/mm/percpu.c b/mm/percpu.c
index 7b40b3963f10..76b9c5e63c56 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -2267,12 +2267,10 @@  void free_percpu(void __percpu *ptr)
 	kmemleak_free_percpu(ptr);
 
 	addr = __pcpu_ptr_to_addr(ptr);
-
-	spin_lock_irqsave(&pcpu_lock, flags);
-
 	chunk = pcpu_chunk_addr_search(addr);
 	off = addr - chunk->base_addr;
 
+	spin_lock_irqsave(&pcpu_lock, flags);
 	size = pcpu_free_area(chunk, off);
 
 	pcpu_memcg_free_hook(chunk, off, size);