| Message ID | 20220210105011.21712-1-cheng-jui.wang@mediatek.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | lockdep: Correct lock_classes index mapping | expand |
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 >
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>
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"); } }
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(-)