linux-next: boottime warning from todays linux-next

linux-next: boottime warning from todays linux-next

[Stephen Rothwell]

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Hi all,

My qemu boot of a powerpc pseries_le_defconfig kernel produced these
kernel messages:

  CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.17.0-rc3 #2
  Call Trace:
  [c0000000073e3a80] [c0000000007bfd40] dump_stack_lvl+0x74/0xa8 (unreliable)
  [c0000000073e3ac0] [c00000000057e3dc] __register_sysctl_table+0x60c/0x9f0
  [c0000000073e3bd0] [c000000002041170] init_fs_stat_sysctls+0x48/0x60
  [c0000000073e3bf0] [c000000000012110] do_one_initcall+0x60/0x2d0
  [c0000000073e3cd0] [c0000000020049f0] kernel_init_freeable+0x334/0x3dc
  [c0000000073e3db0] [c000000000012710] kernel_init+0x30/0x1a0
  [c0000000073e3e10] [c00000000000cd64] ret_from_kernel_thread+0x5c/0x64

Presumably introduced by commit

  b42bc9a3c511 ("Fix regression due to "fs: move binfmt_misc sysctl to its own file"")

-- 
Cheers,
Stephen Rothwell

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Re: linux-next: boottime warning from todays linux-next

[Stephen Rothwell]

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Hi all,

On Thu, 10 Feb 2022 18:43:40 +1100 Stephen Rothwell <sfr@canb.auug.org.au> wrote:
>
> My qemu boot of a powerpc pseries_le_defconfig kernel produced these
> kernel messages:
> 
>   CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.17.0-rc3 #2
>   Call Trace:
>   [c0000000073e3a80] [c0000000007bfd40] dump_stack_lvl+0x74/0xa8 (unreliable)
>   [c0000000073e3ac0] [c00000000057e3dc] __register_sysctl_table+0x60c/0x9f0
>   [c0000000073e3bd0] [c000000002041170] init_fs_stat_sysctls+0x48/0x60
>   [c0000000073e3bf0] [c000000000012110] do_one_initcall+0x60/0x2d0
>   [c0000000073e3cd0] [c0000000020049f0] kernel_init_freeable+0x334/0x3dc
>   [c0000000073e3db0] [c000000000012710] kernel_init+0x30/0x1a0
>   [c0000000073e3e10] [c00000000000cd64] ret_from_kernel_thread+0x5c/0x64
> 
> Presumably introduced by commit
> 
>   b42bc9a3c511 ("Fix regression due to "fs: move binfmt_misc sysctl to its own file"")

OK, I cannot reproduce this with just Linus' tree.  I will try to bisect.

-- 
Cheers,
Stephen Rothwell

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Re: linux-next: boottime warning from todays linux-next

[Stephen Rothwell]

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Hi all,

On Thu, 10 Feb 2022 19:33:02 +1100 Stephen Rothwell <sfr@canb.auug.org.au> wrote:
>
> On Thu, 10 Feb 2022 18:43:40 +1100 Stephen Rothwell <sfr@canb.auug.org.au> wrote:
> >
> > My qemu boot of a powerpc pseries_le_defconfig kernel produced these
> > kernel messages:
> > 
> >   CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.17.0-rc3 #2
> >   Call Trace:
> >   [c0000000073e3a80] [c0000000007bfd40] dump_stack_lvl+0x74/0xa8 (unreliable)
> >   [c0000000073e3ac0] [c00000000057e3dc] __register_sysctl_table+0x60c/0x9f0
> >   [c0000000073e3bd0] [c000000002041170] init_fs_stat_sysctls+0x48/0x60
> >   [c0000000073e3bf0] [c000000000012110] do_one_initcall+0x60/0x2d0
> >   [c0000000073e3cd0] [c0000000020049f0] kernel_init_freeable+0x334/0x3dc
> >   [c0000000073e3db0] [c000000000012710] kernel_init+0x30/0x1a0
> >   [c0000000073e3e10] [c00000000000cd64] ret_from_kernel_thread+0x5c/0x64
> > 
> > Presumably introduced by commit
> > 
> >   b42bc9a3c511 ("Fix regression due to "fs: move binfmt_misc sysctl to its own file"")  
> 
> OK, I cannot reproduce this with just Linus' tree.  I will try to bisect.

It bisected to commit

  43a9443d5da2 ("Merge branch 'akpm-current/current'")

and both parents of that commit are fine :-(

"git diff-tree --cc 43a9443d5da2" looks like this:

43a9443d5da2d53dc06095b90b1aca18b72caef5
diff --cc lib/Kconfig.debug
index f15dd96028b5,efc1a1908e04..682c776ae73d
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@@ -317,6 -339,7 +339,7 @@@ config DEBUG_INFO_BT
  	depends on !DEBUG_INFO_SPLIT && !DEBUG_INFO_REDUCED
  	depends on !GCC_PLUGIN_RANDSTRUCT || COMPILE_TEST
  	depends on BPF_SYSCALL
 -	depends on !DEBUG_INFO_DWARF5
++	depends on !DEBUG_INFO_DWARF5 || PAHOLE_VERSION >= 121
  	help
  	  Generate deduplicated BTF type information from DWARF debug info.
  	  Turning this on expects presence of pahole tool, which will convert
diff --cc tools/include/linux/gfp.h
index b238dbc9eb85,22030756fbc0..56eec4445bc9
--- a/tools/include/linux/gfp.h
+++ b/tools/include/linux/gfp.h
@@@ -2,31 -1,4 +2,30 @@@
  #ifndef _TOOLS_INCLUDE_LINUX_GFP_H
  #define _TOOLS_INCLUDE_LINUX_GFP_H
  
 +#include <linux/types.h>
 +
 +#define __GFP_BITS_SHIFT 26
 +#define __GFP_BITS_MASK ((gfp_t)((1 << __GFP_BITS_SHIFT) - 1))
 +
 +#define __GFP_HIGH		0x20u
 +#define __GFP_IO		0x40u
 +#define __GFP_FS		0x80u
 +#define __GFP_NOWARN		0x200u
 +#define __GFP_ZERO		0x8000u
- #define __GFP_ATOMIC		0x80000u
 +#define __GFP_ACCOUNT		0x100000u
 +#define __GFP_DIRECT_RECLAIM	0x400000u
 +#define __GFP_KSWAPD_RECLAIM	0x2000000u
 +
 +#define __GFP_RECLAIM	(__GFP_DIRECT_RECLAIM | __GFP_KSWAPD_RECLAIM)
 +
 +#define GFP_ZONEMASK	0x0fu
- #define GFP_ATOMIC	(__GFP_HIGH | __GFP_ATOMIC | __GFP_KSWAPD_RECLAIM)
++#define GFP_ATOMIC	(__GFP_HIGH | __GFP_KSWAPD_RECLAIM)
 +#define GFP_KERNEL	(__GFP_RECLAIM | __GFP_IO | __GFP_FS)
 +#define GFP_NOWAIT	(__GFP_KSWAPD_RECLAIM)
 +
 +static inline bool gfpflags_allow_blocking(const gfp_t gfp_flags)
 +{
 +	return !!(gfp_flags & __GFP_DIRECT_RECLAIM);
 +}
 +
  #endif /* _TOOLS_INCLUDE_LINUX_GFP_H */

Which looks pretty innocuous.

-- 
Cheers,
Stephen Rothwell

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Re: linux-next: boottime warning from todays linux-next

[Stephen Rothwell]

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Hi all,

On Thu, 10 Feb 2022 21:41:25 +1100 Stephen Rothwell <sfr@canb.auug.org.au> wrote:
>
> On Thu, 10 Feb 2022 19:33:02 +1100 Stephen Rothwell <sfr@canb.auug.org.au> wrote:
> >
> > On Thu, 10 Feb 2022 18:43:40 +1100 Stephen Rothwell <sfr@canb.auug.org.au> wrote:  
> > >
> > > My qemu boot of a powerpc pseries_le_defconfig kernel produced these
> > > kernel messages:
> > > 
> > >   CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.17.0-rc3 #2
> > >   Call Trace:
> > >   [c0000000073e3a80] [c0000000007bfd40] dump_stack_lvl+0x74/0xa8 (unreliable)
> > >   [c0000000073e3ac0] [c00000000057e3dc] __register_sysctl_table+0x60c/0x9f0
> > >   [c0000000073e3bd0] [c000000002041170] init_fs_stat_sysctls+0x48/0x60
> > >   [c0000000073e3bf0] [c000000000012110] do_one_initcall+0x60/0x2d0
> > >   [c0000000073e3cd0] [c0000000020049f0] kernel_init_freeable+0x334/0x3dc
> > >   [c0000000073e3db0] [c000000000012710] kernel_init+0x30/0x1a0
> > >   [c0000000073e3e10] [c00000000000cd64] ret_from_kernel_thread+0x5c/0x64
> > > 
> > > Presumably introduced by commit
> > > 
> > >   b42bc9a3c511 ("Fix regression due to "fs: move binfmt_misc sysctl to its own file"")    
> > 
> > OK, I cannot reproduce this with just Linus' tree.  I will try to bisect.  
> 
> It bisected to commit
> 
>   43a9443d5da2 ("Merge branch 'akpm-current/current'")
> 
> and both parents of that commit are fine :-(

So it seems that the parent of "fs/binfmt_misc" is a permanently empty
directory - the is_empty_dir() check in insert_header() succeeds.
-- 
Cheers,
Stephen Rothwell

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Re: linux-next: boottime warning from todays linux-next

[Domenico Andreoli]

On Thu, Feb 10, 2022 at 07:33:02PM +1100, Stephen Rothwell wrote:
> Hi all,
> 
> On Thu, 10 Feb 2022 18:43:40 +1100 Stephen Rothwell <sfr@canb.auug.org.au> wrote:
> >
> > My qemu boot of a powerpc pseries_le_defconfig kernel produced these
> > kernel messages:
> > 
> >   CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.17.0-rc3 #2
> >   Call Trace:
> >   [c0000000073e3a80] [c0000000007bfd40] dump_stack_lvl+0x74/0xa8 (unreliable)
> >   [c0000000073e3ac0] [c00000000057e3dc] __register_sysctl_table+0x60c/0x9f0
> >   [c0000000073e3bd0] [c000000002041170] init_fs_stat_sysctls+0x48/0x60
> >   [c0000000073e3bf0] [c000000000012110] do_one_initcall+0x60/0x2d0
> >   [c0000000073e3cd0] [c0000000020049f0] kernel_init_freeable+0x334/0x3dc
> >   [c0000000073e3db0] [c000000000012710] kernel_init+0x30/0x1a0
> >   [c0000000073e3e10] [c00000000000cd64] ret_from_kernel_thread+0x5c/0x64
> > 
> > Presumably introduced by commit
> > 
> >   b42bc9a3c511 ("Fix regression due to "fs: move binfmt_misc sysctl to its own file"")
> 
> OK, I cannot reproduce this with just Linus' tree.  I will try to bisect.

I could not reproduce it on either my amd64 or arm64.

Dom

-- 
rsa4096: 3B10 0CA1 8674 ACBA B4FE  FCD2 CE5B CF17 9960 DE13
ed25519: FFB4 0CC3 7F2E 091D F7DA  356E CC79 2832 ED38 CB05

Re: linux-next: boottime warning from todays linux-next

[Luis Chamberlain]

On Thu, Feb 10, 2022 at 10:29:53PM +1100, Stephen Rothwell wrote:
> Hi all,
> 
> On Thu, 10 Feb 2022 21:41:25 +1100 Stephen Rothwell <sfr@canb.auug.org.au> wrote:
> >
> > On Thu, 10 Feb 2022 19:33:02 +1100 Stephen Rothwell <sfr@canb.auug.org.au> wrote:
> > >
> > > On Thu, 10 Feb 2022 18:43:40 +1100 Stephen Rothwell <sfr@canb.auug.org.au> wrote:  
> > > >
> > > > My qemu boot of a powerpc pseries_le_defconfig kernel produced these
> > > > kernel messages:
> > > > 
> > > >   CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.17.0-rc3 #2
> > > >   Call Trace:
> > > >   [c0000000073e3a80] [c0000000007bfd40] dump_stack_lvl+0x74/0xa8 (unreliable)
> > > >   [c0000000073e3ac0] [c00000000057e3dc] __register_sysctl_table+0x60c/0x9f0
> > > >   [c0000000073e3bd0] [c000000002041170] init_fs_stat_sysctls+0x48/0x60
> > > >   [c0000000073e3bf0] [c000000000012110] do_one_initcall+0x60/0x2d0
> > > >   [c0000000073e3cd0] [c0000000020049f0] kernel_init_freeable+0x334/0x3dc
> > > >   [c0000000073e3db0] [c000000000012710] kernel_init+0x30/0x1a0
> > > >   [c0000000073e3e10] [c00000000000cd64] ret_from_kernel_thread+0x5c/0x64
> > > > 
> > > > Presumably introduced by commit
> > > > 
> > > >   b42bc9a3c511 ("Fix regression due to "fs: move binfmt_misc sysctl to its own file"")    
> > > 
> > > OK, I cannot reproduce this with just Linus' tree.  I will try to bisect.  

OK so that's not the issue.

> > It bisected to commit
> > 
> >   43a9443d5da2 ("Merge branch 'akpm-current/current'")
> > 
> > and both parents of that commit are fine :-(

FWIW Linus merged a more newer version of the regression fix, and only
until today did we get that version on linux-next.

> So it seems that the parent of "fs/binfmt_misc" is a permanently empty
> directory - the is_empty_dir() check in insert_header() succeeds.

I am not seeing this issue on x86_64 KVM guest with:

CONFIG_BINFMT_MISC=m
or
CONFIG_BINFMT_MISC=y

I think the issue might be that linux-next has Andrew's earlier
version of the fix merged, and Linus now has the new version. So
linux-next has these extra things below. But I can't understand
why this is seen on ppc and not on x86_64.

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 241cfc6bc36f..788b9a34d5ab 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -2735,17 +2735,6 @@ static struct ctl_table vm_table[] = {
 	{ }
 };
 
-static struct ctl_table fs_table[] = {
-#if defined(CONFIG_BINFMT_MISC) || defined(CONFIG_BINFMT_MISC_MODULE)
-	{
-		.procname	= "binfmt_misc",
-		.mode		= 0555,
-		.child		= sysctl_mount_point,
-	},
-#endif
-	{ }
-};
-
 static struct ctl_table debug_table[] = {
 #ifdef CONFIG_SYSCTL_EXCEPTION_TRACE
 	{
@@ -2765,7 +2754,6 @@ static struct ctl_table dev_table[] = {
 
 DECLARE_SYSCTL_BASE(kernel, kern_table);
 DECLARE_SYSCTL_BASE(vm, vm_table);
-DECLARE_SYSCTL_BASE(fs, fs_table);
 DECLARE_SYSCTL_BASE(debug, debug_table);
 DECLARE_SYSCTL_BASE(dev, dev_table);
 
@@ -2773,7 +2761,6 @@ int __init sysctl_init_bases(void)
 {
 	register_sysctl_base(kernel);
 	register_sysctl_base(vm);
-	register_sysctl_base(fs);
 	register_sysctl_base(debug);
 	register_sysctl_base(dev);
 

Re: linux-next: boottime warning from todays linux-next

[Tong Zhang]

On Wed, Feb 9, 2022 at 11:43 PM Stephen Rothwell <sfr@canb.auug.org.au> wrote:
>
> Hi all,
>
> My qemu boot of a powerpc pseries_le_defconfig kernel produced these
> kernel messages:
>
>   CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.17.0-rc3 #2
>   Call Trace:
>   [c0000000073e3a80] [c0000000007bfd40] dump_stack_lvl+0x74/0xa8 (unreliable)
>   [c0000000073e3ac0] [c00000000057e3dc] __register_sysctl_table+0x60c/0x9f0
>   [c0000000073e3bd0] [c000000002041170] init_fs_stat_sysctls+0x48/0x60
>   [c0000000073e3bf0] [c000000000012110] do_one_initcall+0x60/0x2d0
>   [c0000000073e3cd0] [c0000000020049f0] kernel_init_freeable+0x334/0x3dc
>   [c0000000073e3db0] [c000000000012710] kernel_init+0x30/0x1a0
>   [c0000000073e3e10] [c00000000000cd64] ret_from_kernel_thread+0x5c/0x64
>
> Presumably introduced by commit
>
>   b42bc9a3c511 ("Fix regression due to "fs: move binfmt_misc sysctl to its own file"")
>
> --
> Cheers,
> Stephen Rothwell

Hi Stephen,
I am trying to see if I can reproduce this.
Could you share the QEMU command line and pseries_le_defconfig?
Latest kernel does not have pseries_le_defconfig so I assume you have
your own version.
Thanks!
- Tong

Re: linux-next: boottime warning from todays linux-next

[Stephen Rothwell]

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Hi Luis,

On Thu, 10 Feb 2022 15:19:09 -0800 Luis Chamberlain <mcgrof@kernel.org> wrote:
> 
> FWIW Linus merged a more newer version of the regression fix, and only
> until today did we get that version on linux-next.
> 
> > So it seems that the parent of "fs/binfmt_misc" is a permanently empty
> > directory - the is_empty_dir() check in insert_header() succeeds.  
> 
> I am not seeing this issue on x86_64 KVM guest with:
> 
> CONFIG_BINFMT_MISC=m
> or
> CONFIG_BINFMT_MISC=y
> 
> I think the issue might be that linux-next has Andrew's earlier
> version of the fix merged, and Linus now has the new version. So
> linux-next has these extra things below. But I can't understand
> why this is seen on ppc and not on x86_64.
> 
> diff --git a/kernel/sysctl.c b/kernel/sysctl.c
> index 241cfc6bc36f..788b9a34d5ab 100644
> --- a/kernel/sysctl.c
> +++ b/kernel/sysctl.c
> @@ -2735,17 +2735,6 @@ static struct ctl_table vm_table[] = {
>  	{ }
>  };
>  
> -static struct ctl_table fs_table[] = {
> -#if defined(CONFIG_BINFMT_MISC) || defined(CONFIG_BINFMT_MISC_MODULE)
> -	{
> -		.procname	= "binfmt_misc",
> -		.mode		= 0555,
> -		.child		= sysctl_mount_point,
> -	},
> -#endif
> -	{ }
> -};
> -
>  static struct ctl_table debug_table[] = {
>  #ifdef CONFIG_SYSCTL_EXCEPTION_TRACE
>  	{
> @@ -2765,7 +2754,6 @@ static struct ctl_table dev_table[] = {
>  
>  DECLARE_SYSCTL_BASE(kernel, kern_table);
>  DECLARE_SYSCTL_BASE(vm, vm_table);
> -DECLARE_SYSCTL_BASE(fs, fs_table);
>  DECLARE_SYSCTL_BASE(debug, debug_table);
>  DECLARE_SYSCTL_BASE(dev, dev_table);
>  
> @@ -2773,7 +2761,6 @@ int __init sysctl_init_bases(void)
>  {
>  	register_sysctl_base(kernel);
>  	register_sysctl_base(vm);
> -	register_sysctl_base(fs);
>  	register_sysctl_base(debug);
>  	register_sysctl_base(dev);
>  

Thanks for noticing that.  I have removed the old version from my copy
of mmotm today.

-- 
Cheers,
Stephen Rothwell

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Re: linux-next: boottime warning from todays linux-next

[Luis Chamberlain]

On Fri, Feb 11, 2022 at 12:33:36PM +1100, Stephen Rothwell wrote:
> Hi Luis,
> 
> On Thu, 10 Feb 2022 15:19:09 -0800 Luis Chamberlain <mcgrof@kernel.org> wrote:
> > 
> > FWIW Linus merged a more newer version of the regression fix, and only
> > until today did we get that version on linux-next.
> > 
> > > So it seems that the parent of "fs/binfmt_misc" is a permanently empty
> > > directory - the is_empty_dir() check in insert_header() succeeds.  
> > 
> > I am not seeing this issue on x86_64 KVM guest with:
> > 
> > CONFIG_BINFMT_MISC=m
> > or
> > CONFIG_BINFMT_MISC=y
> > 
> > I think the issue might be that linux-next has Andrew's earlier
> > version of the fix merged, and Linus now has the new version. So
> > linux-next has these extra things below. But I can't understand
> > why this is seen on ppc and not on x86_64.
> > 
> > diff --git a/kernel/sysctl.c b/kernel/sysctl.c
> > index 241cfc6bc36f..788b9a34d5ab 100644
> > --- a/kernel/sysctl.c
> > +++ b/kernel/sysctl.c
> > @@ -2735,17 +2735,6 @@ static struct ctl_table vm_table[] = {
> >  	{ }
> >  };
> >  
> > -static struct ctl_table fs_table[] = {
> > -#if defined(CONFIG_BINFMT_MISC) || defined(CONFIG_BINFMT_MISC_MODULE)
> > -	{
> > -		.procname	= "binfmt_misc",
> > -		.mode		= 0555,
> > -		.child		= sysctl_mount_point,
> > -	},
> > -#endif
> > -	{ }
> > -};
> > -
> >  static struct ctl_table debug_table[] = {
> >  #ifdef CONFIG_SYSCTL_EXCEPTION_TRACE
> >  	{
> > @@ -2765,7 +2754,6 @@ static struct ctl_table dev_table[] = {
> >  
> >  DECLARE_SYSCTL_BASE(kernel, kern_table);
> >  DECLARE_SYSCTL_BASE(vm, vm_table);
> > -DECLARE_SYSCTL_BASE(fs, fs_table);
> >  DECLARE_SYSCTL_BASE(debug, debug_table);
> >  DECLARE_SYSCTL_BASE(dev, dev_table);
> >  
> > @@ -2773,7 +2761,6 @@ int __init sysctl_init_bases(void)
> >  {
> >  	register_sysctl_base(kernel);
> >  	register_sysctl_base(vm);
> > -	register_sysctl_base(fs);
> >  	register_sysctl_base(debug);
> >  	register_sysctl_base(dev);
> >  
> 
> Thanks for noticing that.  I have removed the old version from my copy
> of mmotm today.

And ... does that fix your boot?

  Luis

Re: linux-next: boottime warning from todays linux-next

[Stephen Rothwell]

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Hi Tong,

On Thu, 10 Feb 2022 15:35:30 -0800 Tong Zhang <ztong0001@gmail.com> wrote:
>
> I am trying to see if I can reproduce this.
> Could you share the QEMU command line and pseries_le_defconfig?
> Latest kernel does not have pseries_le_defconfig so I assume you have
> your own version.

This is a ARCH=powerpc build and qemu run.

qemu-system-ppc64 -M pseries -cpu POWER8 -m 2G -vga none -nographic -kernel $vmlinux -initrd $initrd

I have a simple initrd that just boots to a login prompt.

Anyway, it seems that the mystery has been solved (hopefully).
-- 
Cheers,
Stephen Rothwell

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Re: linux-next: boottime warning from todays linux-next

[Stephen Rothwell]

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Hi Luis,

On Thu, 10 Feb 2022 17:38:22 -0800 Luis Chamberlain <mcgrof@kernel.org> wrote:
>
> On Fri, Feb 11, 2022 at 12:33:36PM +1100, Stephen Rothwell wrote:
> > 
> > Thanks for noticing that.  I have removed the old version from my copy
> > of mmotm today.  
> 
> And ... does that fix your boot?

Yes, the messages are all gone.

Thanks again.
-- 
Cheers,
Stephen Rothwell

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Re: linux-next: boottime warning from todays linux-next

[Tong Zhang]

On Thu, Feb 10, 2022 at 5:43 PM Stephen Rothwell <sfr@canb.auug.org.au> wrote:
>
> Hi Tong,
>
> On Thu, 10 Feb 2022 15:35:30 -0800 Tong Zhang <ztong0001@gmail.com> wrote:
> >
> > I am trying to see if I can reproduce this.
> > Could you share the QEMU command line and pseries_le_defconfig?
> > Latest kernel does not have pseries_le_defconfig so I assume you have
> > your own version.
>
> This is a ARCH=powerpc build and qemu run.
>
> qemu-system-ppc64 -M pseries -cpu POWER8 -m 2G -vga none -nographic -kernel $vmlinux -initrd $initrd
>
> I have a simple initrd that just boots to a login prompt.
>
> Anyway, it seems that the mystery has been solved (hopefully).
> --
> Cheers,
> Stephen Rothwell

Thanks for providing the configuration.
I tried the same setup and it worked. No crash whatsoever.

As mentioned by Luis, if I enable the line below, the kernel will
throw out a similar message like in your original mail.

@@ -2773,7 +2761,6 @@ int __init sysctl_init_bases(void)
{
register_sysctl_base(kernel);
register_sysctl_base(vm);
+ register_sysctl_base(fs);
register_sysctl_base(debug);
register_sysctl_base(dev);

[    0.190779][    T1] Call Trace:
[    0.190836][    T1] [c0000000073e3a90] [c0000000007bc2e0]
dump_stack_lvl+0x74/0xa8 (unreliable)
[    0.190940][    T1] [c0000000073e3ad0] [c000000000581d9c]
__register_sysctl_table+0x59c/0x8f0
[    0.191054][    T1] [c0000000073e3bd0] [c0000000020416fc]
init_fs_stat_sysctls+0x48/0x60
[    0.191110][    T1] [c0000000073e3bf0] [c000000000012190]
do_one_initcall+0x60/0x2c0
[    0.191139][    T1] [c0000000073e3cc0] [c000000002004a24]
kernel_init_freeable+0x33c/0x3dc
[    0.191189][    T1] [c0000000073e3da0] [c0000000000127a4]
kernel_init+0x34/0x1a0
[    0.191231][    T1] [c0000000073e3e10] [c00000000000cd64]
ret_from_kernel_thread+0x5c/0x64

I believe this issue can be marked as resolved now.

- Tong

Re: linux-next: boottime warning from todays linux-next

[Luis Chamberlain]

On Fri, Feb 11, 2022 at 06:46:47PM +1100, Stephen Rothwell wrote:
> Hi Luis,
> 
> On Thu, 10 Feb 2022 17:38:22 -0800 Luis Chamberlain <mcgrof@kernel.org> wrote:
> >
> > On Fri, Feb 11, 2022 at 12:33:36PM +1100, Stephen Rothwell wrote:
> > > 
> > > Thanks for noticing that.  I have removed the old version from my copy
> > > of mmotm today.  
> > 
> > And ... does that fix your boot?
> 
> Yes, the messages are all gone.

Fantastic, thanks for the confirmation!

OK so now a side independent curiousity remains though. Double sysctl
registration should not happen. But if someone introduces a bug by doing
that, it seems to not crash on x86. But it does cause a crash or a
kernel warning on ppc.

Why?

And I think we should just WARN_ONCE() for this case, and make the
issue clearer so that if it happens again, folks don't go scrambling
as if chickens running around with their heads cut off.

  Luis

Re: linux-next: boottime warning from todays linux-next

[Tong Zhang]

On Fri, Feb 11, 2022 at 10:51 AM Luis Chamberlain <mcgrof@kernel.org> wrote:
>
> On Fri, Feb 11, 2022 at 06:46:47PM +1100, Stephen Rothwell wrote:
> > Hi Luis,
> >
> > On Thu, 10 Feb 2022 17:38:22 -0800 Luis Chamberlain <mcgrof@kernel.org> wrote:
> > >
> > > On Fri, Feb 11, 2022 at 12:33:36PM +1100, Stephen Rothwell wrote:
> > > >
> > > > Thanks for noticing that.  I have removed the old version from my copy
> > > > of mmotm today.
> > >
> > > And ... does that fix your boot?
> >
> > Yes, the messages are all gone.
>
> Fantastic, thanks for the confirmation!
>
> OK so now a side independent curiousity remains though. Double sysctl
> registration should not happen. But if someone introduces a bug by doing
> that, it seems to not crash on x86. But it does cause a crash or a
> kernel warning on ppc.
>

IMO this is ARCH irrelevant, it will definitely give the same result
on double registration.

Tested on a x86 using the same double registration code.

[    1.098835] Call Trace:
[    1.098835]  <TASK>
[    1.098835]  dump_stack_lvl+0x34/0x44
[    1.098835]  __register_sysctl_table+0x6f4/0x720
[    1.098835]  ? early_memunmap+0x5/0x5
[    1.098835]  init_fs_stat_sysctls+0x3e/0x41
[    1.098835]  do_one_initcall+0x82/0x280
[    1.098835]  ? trace_event_raw_event_initcall_finish+0x150/0x150
[    1.098835]  ? parameq+0x80/0x80
[    1.098835]  ? _raw_spin_unlock_irq+0x20/0x30
[    1.098835]  ? create_object+0x395/0x510
[    1.098835]  kernel_init_freeable+0x2a5/0x2fe
[    1.098835]  ? rest_init+0xe0/0xe0
[    1.098835]  kernel_init+0x14/0x130
[    1.098835]  ret_from_fork+0x1f/0x30
[    1.098835]  </TASK>

However this is not a fatal error and the kernel is still operable in
both PPC and X86 cases, the bug can be catched and we can use
WARN_ONCE().

> Why?
>
> And I think we should just WARN_ONCE() for this case, and make the
> issue clearer so that if it happens again, folks don't go scrambling
> as if chickens running around with their heads cut off.
>
>   Luis


- Tong