* [PATCH] lockdep: Correct lock_classes index mapping
@ 2022-02-10 10:50 Cheng Jui Wang
2022-02-10 12:45 ` Boqun Feng
2022-02-10 12:53 ` Greg KH
0 siblings, 2 replies; 3+ messages in thread
From: Cheng Jui Wang @ 2022-02-10 10:50 UTC (permalink / raw)
To: Peter Zijlstra, Ingo Molnar
Cc: Will Deacon, Waiman Long, Boqun Feng, Matthias Brugger,
linux-kernel, linux-arm-kernel, linux-mediatek, stable,
wsd_upstream, Eason-YH Lin, Kobe-CP Wu, Jeff-CC Hsu,
Cheng Jui Wang
A kernel exception was hit when trying to dump /proc/lockdep_chains after
lockdep report "BUG: MAX_LOCKDEP_CHAIN_HLOCKS too low!":
Unable to handle kernel paging request at virtual address 00054005450e05c3
...
00054005450e05c3] address between user and kernel address ranges
...
pc : [0xffffffece769b3a8] string+0x50/0x10c
lr : [0xffffffece769ac88] vsnprintf+0x468/0x69c
...
Call trace:
string+0x50/0x10c
vsnprintf+0x468/0x69c
seq_printf+0x8c/0xd8
print_name+0x64/0xf4
lc_show+0xb8/0x128
seq_read_iter+0x3cc/0x5fc
proc_reg_read_iter+0xdc/0x1d4
The cause of the problem is the function lock_chain_get_class() will
shift lock_classes index by 1, but the index don't need to be shifted
anymore since commit 01bb6f0af992 ("locking/lockdep: Change the range of
class_idx in held_lock struct") already change the index to start from
0.
The lock_classes[-1] located at chain_hlocks array. When printing
lock_classes[-1] after the chain_hlocks entries are modified, the
exception happened.
The output of lockdep_chains are incorrect due to this problem too.
Fixes: f611e8cf98ec ("lockdep: Take read/write status in consideration when generate chainkey")
Signed-off-by: Cheng Jui Wang <cheng-jui.wang@mediatek.com>
---
kernel/locking/lockdep.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 4a882f83aeb9..f8a0212189ca 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -3462,7 +3462,7 @@ struct lock_class *lock_chain_get_class(struct lock_chain *chain, int i)
u16 chain_hlock = chain_hlocks[chain->base + i];
unsigned int class_idx = chain_hlock_class_idx(chain_hlock);
- return lock_classes + class_idx - 1;
+ return lock_classes + class_idx;
}
/*
@@ -3530,7 +3530,7 @@ static void print_chain_keys_chain(struct lock_chain *chain)
hlock_id = chain_hlocks[chain->base + i];
chain_key = print_chain_key_iteration(hlock_id, chain_key);
- print_lock_name(lock_classes + chain_hlock_class_idx(hlock_id) - 1);
+ print_lock_name(lock_classes + chain_hlock_class_idx(hlock_id));
printk("\n");
}
}
--
2.18.0
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] lockdep: Correct lock_classes index mapping
2022-02-10 10:50 [PATCH] lockdep: Correct lock_classes index mapping Cheng Jui Wang
@ 2022-02-10 12:45 ` Boqun Feng
2022-02-10 12:53 ` Greg KH
1 sibling, 0 replies; 3+ messages in thread
From: Boqun Feng @ 2022-02-10 12:45 UTC (permalink / raw)
To: Cheng Jui Wang
Cc: Peter Zijlstra, Ingo Molnar, Will Deacon, Waiman Long,
Matthias Brugger, linux-kernel, linux-arm-kernel, linux-mediatek,
stable, wsd_upstream, Eason-YH Lin, Kobe-CP Wu, Jeff-CC Hsu
[-- Attachment #1: Type: text/plain, Size: 2584 bytes --]
On Thu, Feb 10, 2022 at 06:50:11PM +0800, Cheng Jui Wang wrote:
> A kernel exception was hit when trying to dump /proc/lockdep_chains after
> lockdep report "BUG: MAX_LOCKDEP_CHAIN_HLOCKS too low!":
>
> Unable to handle kernel paging request at virtual address 00054005450e05c3
> ...
> 00054005450e05c3] address between user and kernel address ranges
> ...
> pc : [0xffffffece769b3a8] string+0x50/0x10c
> lr : [0xffffffece769ac88] vsnprintf+0x468/0x69c
> ...
> Call trace:
> string+0x50/0x10c
> vsnprintf+0x468/0x69c
> seq_printf+0x8c/0xd8
> print_name+0x64/0xf4
> lc_show+0xb8/0x128
> seq_read_iter+0x3cc/0x5fc
> proc_reg_read_iter+0xdc/0x1d4
>
> The cause of the problem is the function lock_chain_get_class() will
> shift lock_classes index by 1, but the index don't need to be shifted
> anymore since commit 01bb6f0af992 ("locking/lockdep: Change the range of
> class_idx in held_lock struct") already change the index to start from
> 0.
>
> The lock_classes[-1] located at chain_hlocks array. When printing
> lock_classes[-1] after the chain_hlocks entries are modified, the
> exception happened.
>
> The output of lockdep_chains are incorrect due to this problem too.
>
> Fixes: f611e8cf98ec ("lockdep: Take read/write status in consideration when generate chainkey")
>
> Signed-off-by: Cheng Jui Wang <cheng-jui.wang@mediatek.com>
Hmm.. this means that the /proc/lockdep_chains has been incorrect since
commit f611e8cf89ec..
Nice catch!
Reviewed-by: Boqun Feng <boqun.feng@gmail.com>
Regards,
Boqun
> ---
> kernel/locking/lockdep.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
> index 4a882f83aeb9..f8a0212189ca 100644
> --- a/kernel/locking/lockdep.c
> +++ b/kernel/locking/lockdep.c
> @@ -3462,7 +3462,7 @@ struct lock_class *lock_chain_get_class(struct lock_chain *chain, int i)
> u16 chain_hlock = chain_hlocks[chain->base + i];
> unsigned int class_idx = chain_hlock_class_idx(chain_hlock);
>
> - return lock_classes + class_idx - 1;
> + return lock_classes + class_idx;
> }
>
> /*
> @@ -3530,7 +3530,7 @@ static void print_chain_keys_chain(struct lock_chain *chain)
> hlock_id = chain_hlocks[chain->base + i];
> chain_key = print_chain_key_iteration(hlock_id, chain_key);
>
> - print_lock_name(lock_classes + chain_hlock_class_idx(hlock_id) - 1);
> + print_lock_name(lock_classes + chain_hlock_class_idx(hlock_id));
> printk("\n");
> }
> }
> --
> 2.18.0
>
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^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] lockdep: Correct lock_classes index mapping
2022-02-10 10:50 [PATCH] lockdep: Correct lock_classes index mapping Cheng Jui Wang
2022-02-10 12:45 ` Boqun Feng
@ 2022-02-10 12:53 ` Greg KH
1 sibling, 0 replies; 3+ messages in thread
From: Greg KH @ 2022-02-10 12:53 UTC (permalink / raw)
To: Cheng Jui Wang
Cc: Peter Zijlstra, Ingo Molnar, Will Deacon, Waiman Long,
Boqun Feng, Matthias Brugger, linux-kernel, linux-arm-kernel,
linux-mediatek, stable, wsd_upstream, Eason-YH Lin, Kobe-CP Wu,
Jeff-CC Hsu
On Thu, Feb 10, 2022 at 06:50:11PM +0800, Cheng Jui Wang wrote:
> A kernel exception was hit when trying to dump /proc/lockdep_chains after
> lockdep report "BUG: MAX_LOCKDEP_CHAIN_HLOCKS too low!":
>
> Unable to handle kernel paging request at virtual address 00054005450e05c3
> ...
> 00054005450e05c3] address between user and kernel address ranges
> ...
> pc : [0xffffffece769b3a8] string+0x50/0x10c
> lr : [0xffffffece769ac88] vsnprintf+0x468/0x69c
> ...
> Call trace:
> string+0x50/0x10c
> vsnprintf+0x468/0x69c
> seq_printf+0x8c/0xd8
> print_name+0x64/0xf4
> lc_show+0xb8/0x128
> seq_read_iter+0x3cc/0x5fc
> proc_reg_read_iter+0xdc/0x1d4
>
> The cause of the problem is the function lock_chain_get_class() will
> shift lock_classes index by 1, but the index don't need to be shifted
> anymore since commit 01bb6f0af992 ("locking/lockdep: Change the range of
> class_idx in held_lock struct") already change the index to start from
> 0.
>
> The lock_classes[-1] located at chain_hlocks array. When printing
> lock_classes[-1] after the chain_hlocks entries are modified, the
> exception happened.
>
> The output of lockdep_chains are incorrect due to this problem too.
>
> Fixes: f611e8cf98ec ("lockdep: Take read/write status in consideration when generate chainkey")
>
> Signed-off-by: Cheng Jui Wang <cheng-jui.wang@mediatek.com>
> ---
> kernel/locking/lockdep.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
> index 4a882f83aeb9..f8a0212189ca 100644
> --- a/kernel/locking/lockdep.c
> +++ b/kernel/locking/lockdep.c
> @@ -3462,7 +3462,7 @@ struct lock_class *lock_chain_get_class(struct lock_chain *chain, int i)
> u16 chain_hlock = chain_hlocks[chain->base + i];
> unsigned int class_idx = chain_hlock_class_idx(chain_hlock);
>
> - return lock_classes + class_idx - 1;
> + return lock_classes + class_idx;
> }
>
> /*
> @@ -3530,7 +3530,7 @@ static void print_chain_keys_chain(struct lock_chain *chain)
> hlock_id = chain_hlocks[chain->base + i];
> chain_key = print_chain_key_iteration(hlock_id, chain_key);
>
> - print_lock_name(lock_classes + chain_hlock_class_idx(hlock_id) - 1);
> + print_lock_name(lock_classes + chain_hlock_class_idx(hlock_id));
> printk("\n");
> }
> }
> --
> 2.18.0
>
<formletter>
This is not the correct way to submit patches for inclusion in the
stable kernel tree. Please read:
https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
for how to do this properly.
</formletter>
^ permalink raw reply [flat|nested] 3+ messages in thread
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2022-02-10 12:45 ` Boqun Feng
2022-02-10 12:53 ` Greg KH
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