Re: [PATCH v2 5/5] dump_stack: unify debug information printed byshow_regs()

From: Vineet Gupta
Date: Sat Mar 30 2013 - 02:14:00 EST

Hi Tejun,

On 03/30/2013 08:54 AM, Tejun Heo wrote:
> show_regs() is inherently arch-dependent but it does make sense to
> print generic debug information and some archs already do albeit in
> slightly different forms. This patch introduces a generic function to
> print debug information from show_regs() so that different archs print
> out the same information and it's much easier to modify what's
> printed.
>
> show_regs_print_current() prints out the same debug info as
> dump_stack() does plus CPU, task and thread_info pointers.
>
> * Archs which didn't print debug info now do.
>
> alpha, arc, blackfin, c6x, cris, frv, h8300, hexagon, ia64, m32r,
> metag, microblaze, mn10300, openrisc, parisc, score, sh64, sparc,
> um, xtensa
>
> * Already prints debug info. Replaced with show_regs_print_current().
> The printed information is superset of what used to be there.
>
> arm, arm64, avr32, mips, powerpc, sh32, tile, unicore32, x86
>
> * The printed debug information includes arch-specific bits. Left
> alone.
>
> s390
>
> Note that now all archs print the debug info before actual register
> dumps.
>
> An example BUG() dump follows.
>
> kernel BUG at /work/os/work/kernel/workqueue.c:4841!
> invalid opcode: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC
> Modules linked in:
> Pid: 1, comm: swapper/0 Tainted: G W 3.9.0-rc1-work+ #20 empty empty/S3992
> CPU:0 task: ffff88007c85e040 ti: ffff88007c860000 task.ti: ffff88007c860000
> RIP: 0010:[<ffffffff8234a042>] [<ffffffff8234a042>] init_workqueues+0x15/0x17
> RSP: 0000:ffff88007c861ec8 EFLAGS: 00010296
> RAX: 0000000000000024 RBX: ffffffff82446608 RCX: 0000000000000001
> RDX: 0000000000000046 RSI: 0000000000000000 RDI: 0000000000000009
> RBP: ffff88007c861ec8 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000001 R11: 0000000000000000 R12: ffffffff8234a02d
> R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
> FS: 0000000000000000(0000) GS:ffff88007dc00000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
> CR2: ffff88015f7ff000 CR3: 00000000021f1000 CR4: 00000000000007f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
> Stack:
> ffff88007c861ef8 ffffffff81000312 ffffffff82446608 ffff88007c85e650
> 0000000000000003 0000000000000000 ffff88007c861f38 ffffffff82335e5d
> ffff88007c862080 ffffffff8223d8c0 ffff88007c862080 ffffffff81c47730
> Call Trace:
> [<ffffffff81000312>] do_one_initcall+0x122/0x170
> [<ffffffff82335e5d>] kernel_init_freeable+0x9b/0x1c8
> ...
>
> v2: Typo fix in x86-32.
>
> Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
> ---
> Silly last minute mistake in x86-32. git branch updated accordingly.
>
> Thanks.
>
> arch/alpha/kernel/process.c | 1 +
> arch/arc/kernel/troubleshoot.c | 1 +
> arch/arm/kernel/process.c | 8 ++------
> arch/arm64/kernel/process.c | 7 +------
> arch/avr32/kernel/process.c | 5 ++---
> arch/blackfin/kernel/trace.c | 2 ++
> arch/c6x/kernel/traps.c | 1 +
> arch/cris/arch-v10/kernel/process.c | 3 +++
> arch/cris/arch-v32/kernel/process.c | 3 +++
> arch/frv/kernel/traps.c | 3 +--
> arch/h8300/kernel/process.c | 2 ++
> arch/hexagon/kernel/vm_events.c | 2 ++
> arch/ia64/kernel/process.c | 4 ++--
> arch/m32r/kernel/process.c | 2 ++
> arch/metag/kernel/process.c | 2 ++
> arch/microblaze/kernel/process.c | 2 ++
> arch/mips/kernel/traps.c | 2 +-
> arch/mn10300/kernel/process.c | 1 +
> arch/openrisc/kernel/process.c | 1 +
> arch/parisc/kernel/traps.c | 2 ++
> arch/powerpc/kernel/process.c | 8 ++------
> arch/score/kernel/traps.c | 2 ++
> arch/sh/kernel/process_32.c | 6 +-----
> arch/sh/kernel/process_64.c | 1 +
> arch/sparc/kernel/process_32.c | 2 ++
> arch/sparc/kernel/process_64.c | 2 ++
> arch/tile/kernel/process.c | 3 +--
> arch/um/sys-ppc/sysrq.c | 2 ++
> arch/unicore32/kernel/process.c | 6 +-----
> arch/x86/include/asm/bug.h | 3 ---
> arch/x86/kernel/dumpstack_32.c | 4 +---
> arch/x86/kernel/dumpstack_64.c | 6 +-----
> arch/x86/kernel/process.c | 24 ------------------------
> arch/x86/kernel/process_32.c | 2 --
> arch/x86/kernel/process_64.c | 1 -
> arch/xtensa/kernel/traps.c | 2 ++
> include/linux/printk.h | 2 ++
> lib/dump_stack.c | 16 ++++++++++++++++
> 38 files changed, 70 insertions(+), 76 deletions(-)
>
[..]
>
> diff --git a/arch/arc/kernel/troubleshoot.c b/arch/arc/kernel/troubleshoot.c
> index 7c10873..96be1e6 100644
> --- a/arch/arc/kernel/troubleshoot.c
> +++ b/arch/arc/kernel/troubleshoot.c
> @@ -163,6 +163,7 @@ void show_regs(struct pt_regs *regs)
> return;
>
> print_task_path_n_nm(tsk, buf);
> + show_regs_print_info(KERN_INFO);
>
> if (current->thread.cause_code)
> show_ecr_verbose(regs);

With print-fatal-signals enabled, this will also be called for dumping user mode
register state. With your patch, we now get something like this

----------->8-------------------------
[ARCLinux]$ ./crash
crash/50: potentially unexpected fatal signal 11. <-- [1]
/sbin/crash, TGID 50 <-- [2]
Pid: 50, comm: crash Not tainted 3.9.0-rc4+ #132 <-- [3]
CPU:0 task: 8e11c2c0 ti: 8e136000 task.ti: 8e136000

[ECR]: 0x00230400 => Misaligned r/w from 0x0001036a
[EFA]: 0x0001036a
[ERET]: 0x0001036a (PC of Faulting Instr)
...
...
----------->8-------------------------

Clearly there's duplication (rather triplication) of task name and tgid output.

Although in line [2], ARC trouble-shooting code prints the task path (rather than
comm). This was done to help identify faulting LTP open posix tests with same name
in different directories: e.g. fork/6-1, sigqueue/6-1 ....
Is this something you want to add to generic code as well - although it's slightly
involved due to tsk/mm locking etc.

Also I personally prefer the more compact <task-nm>/<tgid> format of [1] vs. [3].

Anyhow, can you please fold the following into your patchset to reduce above
duplication.

------------------->