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    SubjectRe: [PATCH v2 5/5] dump_stack: unify debug information printed by show_regs()
    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@kernel.org>
    > ---
    > 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.

    ------------------->
    From 15e8d65f35385148f81d87aadadd7791ba79663c Mon Sep 17 00:00:00 2001
    From: Vineet Gupta <vgupta@synopsys.com>
    Date: Sat, 30 Mar 2013 11:35:23 +0530
    Subject: [PATCH] print-fatal-signals: reduce duplicated information

    ----------->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]
    ...
    ----------->8------------

    Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
    ---
    arch/arc/kernel/troubleshoot.c | 2 +-
    kernel/signal.c | 3 +--
    2 files changed, 2 insertions(+), 3 deletions(-)

    diff --git a/arch/arc/kernel/troubleshoot.c b/arch/arc/kernel/troubleshoot.c
    index 96be1e6..0aec0198 100644
    --- a/arch/arc/kernel/troubleshoot.c
    +++ b/arch/arc/kernel/troubleshoot.c
    @@ -71,7 +71,7 @@ void print_task_path_n_nm(struct task_struct *tsk, char *buf)
    }

    done:
    - pr_info("%s, TGID %u\n", path_nm, tsk->tgid);
    + pr_info("Path: %s\n", path_nm);
    }
    EXPORT_SYMBOL(print_task_path_n_nm);

    diff --git a/kernel/signal.c b/kernel/signal.c
    index dd72567..9c4ef65 100644
    --- a/kernel/signal.c
    +++ b/kernel/signal.c
    @@ -1160,8 +1160,7 @@ static int send_signal(int sig, struct siginfo *info, struct
    task_struct *t,
    static void print_fatal_signal(int signr)
    {
    struct pt_regs *regs = signal_pt_regs();
    - printk(KERN_INFO "%s/%d: potentially unexpected fatal signal %d.\n",
    - current->comm, task_pid_nr(current), signr);
    + printk(KERN_INFO "potentially unexpected fatal signal %d.\n", signr);

    #if defined(__i386__) && !defined(__arch_um__)
    printk(KERN_INFO "code at %08lx: ", regs->ip);
    --
    1.7.10.4



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