csdlock_debug uses early_param and static_branch_enable() to enable
csd_lock_wait feature, which triggers a panic on arm64 with config:
CONFIG_SPARSEMEM=y
CONFIG_SPARSEMEM_VMEMMAP=n
With CONFIG_SPARSEMEM_VMEMMAP=n, __nr_to_section is called in
static_key_enable() and returns NULL which makes NULL dereference
because mem_section is initialized in sparse_init() which is later
than parse_early_param() stage.
For powerpc this is also broken, because early_param stage is
earlier than jump_label_init() so static_key_enable won't work.
powerpc throws an warning: "static key 'xxx' used before call
to jump_label_init()".
Thus, early_param is too early for csd_lock_wait to run
static_branch_enable(), so changes it to __setup to fix these.
Fixes: 8d0968cc6b8f ("locking/csd_lock: Add boot parameter for controlling CSD lock debugging")
Cc: [email protected]
Reported-by: Chen jingwen <[email protected]>
Signed-off-by: Chen Zhongjin <[email protected]>
---
Change v3 -> v4:
Fix title and description because this fix is also applied
to powerpc.
For more detailed arm64 bug report see:
https://lore.kernel.org/linux-arm-kernel/[email protected]/t/
Change v2 -> v3:
Add module name in title
Change v1 -> v2:
Fix return 1 for __setup
---
kernel/smp.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/kernel/smp.c b/kernel/smp.c
index 65a630f62363..381eb15cd28f 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -174,9 +174,9 @@ static int __init csdlock_debug(char *str)
if (val)
static_branch_enable(&csdlock_debug_enabled);
- return 0;
+ return 1;
}
-early_param("csdlock_debug", csdlock_debug);
+__setup("csdlock_debug=", csdlock_debug);
static DEFINE_PER_CPU(call_single_data_t *, cur_csd);
static DEFINE_PER_CPU(smp_call_func_t, cur_csd_func);
--
2.17.1
On 2022/5/10 17:46, Chen Zhongjin wrote:
> csdlock_debug uses early_param and static_branch_enable() to enable
> csd_lock_wait feature, which triggers a panic on arm64 with config:
> CONFIG_SPARSEMEM=y
> CONFIG_SPARSEMEM_VMEMMAP=n
>
> With CONFIG_SPARSEMEM_VMEMMAP=n, __nr_to_section is called in
> static_key_enable() and returns NULL which makes NULL dereference
> because mem_section is initialized in sparse_init() which is later
> than parse_early_param() stage.
>
> For powerpc this is also broken, because early_param stage is
> earlier than jump_label_init() so static_key_enable won't work.
> powerpc throws an warning: "static key 'xxx' used before call
> to jump_label_init()".
>
> Thus, early_param is too early for csd_lock_wait to run
> static_branch_enable(), so changes it to __setup to fix these.
>
> Fixes: 8d0968cc6b8f ("locking/csd_lock: Add boot parameter for controlling CSD lock debugging")
> Cc: [email protected]
> Reported-by: Chen jingwen <[email protected]>
> Signed-off-by: Chen Zhongjin <[email protected]>
> ---
> Change v3 -> v4:
> Fix title and description because this fix is also applied
> to powerpc.
> For more detailed arm64 bug report see:
> https://lore.kernel.org/linux-arm-kernel/[email protected]/t/
>
> Change v2 -> v3:
> Add module name in title
>
> Change v1 -> v2:
> Fix return 1 for __setup
> ---
> kernel/smp.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/smp.c b/kernel/smp.c
> index 65a630f62363..381eb15cd28f 100644
> --- a/kernel/smp.c
> +++ b/kernel/smp.c
> @@ -174,9 +174,9 @@ static int __init csdlock_debug(char *str)
> if (val)
> static_branch_enable(&csdlock_debug_enabled);
>
> - return 0;
> + return 1;
> }
> -early_param("csdlock_debug", csdlock_debug);
> +__setup("csdlock_debug=", csdlock_debug);
>
> static DEFINE_PER_CPU(call_single_data_t *, cur_csd);
> static DEFINE_PER_CPU(smp_call_func_t, cur_csd_func);
Ping for review. Thanks！
On Tue, May 17, 2022 at 11:22:04AM +0800, Chen Zhongjin wrote:
> On 2022/5/10 17:46, Chen Zhongjin wrote:
> > csdlock_debug uses early_param and static_branch_enable() to enable
> > csd_lock_wait feature, which triggers a panic on arm64 with config:
> > CONFIG_SPARSEMEM=y
> > CONFIG_SPARSEMEM_VMEMMAP=n
> >
> > With CONFIG_SPARSEMEM_VMEMMAP=n, __nr_to_section is called in
> > static_key_enable() and returns NULL which makes NULL dereference
> > because mem_section is initialized in sparse_init() which is later
> > than parse_early_param() stage.
> >
> > For powerpc this is also broken, because early_param stage is
> > earlier than jump_label_init() so static_key_enable won't work.
> > powerpc throws an warning: "static key 'xxx' used before call
> > to jump_label_init()".
> >
> > Thus, early_param is too early for csd_lock_wait to run
> > static_branch_enable(), so changes it to __setup to fix these.
> >
> > Fixes: 8d0968cc6b8f ("locking/csd_lock: Add boot parameter for controlling CSD lock debugging")
> > Cc: [email protected]
> > Reported-by: Chen jingwen <[email protected]>
> > Signed-off-by: Chen Zhongjin <[email protected]>
> > ---
> > Change v3 -> v4:
> > Fix title and description because this fix is also applied
> > to powerpc.
> > For more detailed arm64 bug report see:
> > https://lore.kernel.org/linux-arm-kernel/[email protected]/t/
> >
> > Change v2 -> v3:
> > Add module name in title
> >
> > Change v1 -> v2:
> > Fix return 1 for __setup
> > ---
> > kernel/smp.c | 4 ++--
> > 1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/kernel/smp.c b/kernel/smp.c
> > index 65a630f62363..381eb15cd28f 100644
> > --- a/kernel/smp.c
> > +++ b/kernel/smp.c
> > @@ -174,9 +174,9 @@ static int __init csdlock_debug(char *str)
> > if (val)
> > static_branch_enable(&csdlock_debug_enabled);
> >
> > - return 0;
> > + return 1;
> > }
> > -early_param("csdlock_debug", csdlock_debug);
> > +__setup("csdlock_debug=", csdlock_debug);
> >
> > static DEFINE_PER_CPU(call_single_data_t *, cur_csd);
> > static DEFINE_PER_CPU(smp_call_func_t, cur_csd_func);
>
> Ping for review. Thanks！
I have pulled it into -rcu for testing and further review. It might
well need to go through some other path, though.
Thanx, Paul
On Fri, May 27, 2022 at 02:49:03PM +0800, Chen Zhongjin wrote:
> Hi,
>
> On 2022/5/18 9:11, Paul E. McKenney wrote:
> > On Tue, May 17, 2022 at 11:22:04AM +0800, Chen Zhongjin wrote:
> >> On 2022/5/10 17:46, Chen Zhongjin wrote:
> >>> csdlock_debug uses early_param and static_branch_enable() to enable
> >>> csd_lock_wait feature, which triggers a panic on arm64 with config:
> >>> CONFIG_SPARSEMEM=y
> >>> CONFIG_SPARSEMEM_VMEMMAP=n
> >>>
> >>> With CONFIG_SPARSEMEM_VMEMMAP=n, __nr_to_section is called in
> >>> static_key_enable() and returns NULL which makes NULL dereference
> >>> because mem_section is initialized in sparse_init() which is later
> >>> than parse_early_param() stage.
> >>>
> >>> For powerpc this is also broken, because early_param stage is
> >>> earlier than jump_label_init() so static_key_enable won't work.
> >>> powerpc throws an warning: "static key 'xxx' used before call
> >>> to jump_label_init()".
> >>>
> >>> Thus, early_param is too early for csd_lock_wait to run
> >>> static_branch_enable(), so changes it to __setup to fix these.
> >>>
> >>> Fixes: 8d0968cc6b8f ("locking/csd_lock: Add boot parameter for controlling CSD lock debugging")
> >>> Cc: [email protected]
> >>> Reported-by: Chen jingwen <[email protected]>
> >>> Signed-off-by: Chen Zhongjin <[email protected]>
> >>> ---
> >>> Change v3 -> v4:
> >>> Fix title and description because this fix is also applied
> >>> to powerpc.
> >>> For more detailed arm64 bug report see:
> >>> https://lore.kernel.org/linux-arm-kernel/[email protected]/t/
> >>>
> >>> Change v2 -> v3:
> >>> Add module name in title
> >>>
> >>> Change v1 -> v2:
> >>> Fix return 1 for __setup
> >>> ---
> >>> kernel/smp.c | 4 ++--
> >>> 1 file changed, 2 insertions(+), 2 deletions(-)
> >>>
> >>> diff --git a/kernel/smp.c b/kernel/smp.c
> >>> index 65a630f62363..381eb15cd28f 100644
> >>> --- a/kernel/smp.c
> >>> +++ b/kernel/smp.c
> >>> @@ -174,9 +174,9 @@ static int __init csdlock_debug(char *str)
> >>> if (val)
> >>> static_branch_enable(&csdlock_debug_enabled);
> >>>
> >>> - return 0;
> >>> + return 1;
> >>> }
> >>> -early_param("csdlock_debug", csdlock_debug);
> >>> +__setup("csdlock_debug=", csdlock_debug);
> >>>
> >>> static DEFINE_PER_CPU(call_single_data_t *, cur_csd);
> >>> static DEFINE_PER_CPU(smp_call_func_t, cur_csd_func);
> >>
> >> Ping for review. Thanks！
> >
> > I have pulled it into -rcu for testing and further review. It might
> > well need to go through some other path, though.
> >> Thanx, Paul
> > .
>
> So did it have any result? Do we have any idea to fix that except delaying the
> set timing? I guess that maybe not using static_branch can work for this, but it
> still needs to be evaluated for performance influence of not enabled situation.
It was in -next for a short time without complaints. It will go back
into -next after the merge window closes. If there are no objections,
I would include it in my pull request for the next merge window (v5.20).
Thanx, Paul