From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Changbin Du <changbin.du@gmail.com>
Cc: Jiri Slaby <jirislaby@kernel.org>,
Palmer Dabbelt <palmer@dabbelt.com>,
linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org
Subject: Re: [PATCH] sysrq: do not omit current cpu when showing backtrace of all active CPUs
Date: Tue, 26 Apr 2022 13:24:58 +0200 [thread overview]
Message-ID: <YmfWipwuVlAt5Meq@kroah.com> (raw)
In-Reply-To: <20220118003358.6pcowtbds44dntls@mail.google.com>
On Tue, Jan 18, 2022 at 08:33:58AM +0800, Changbin Du wrote:
> Hi, Greg,
> On Mon, Jan 17, 2022 at 04:50:21PM +0100, Greg Kroah-Hartman wrote:
> > On Mon, Jan 17, 2022 at 11:43:00PM +0800, Changbin Du wrote:
> > > The backtrace of current CPU also should be printed as it is active. This
> > > change add stack trace for current CPU and print a hint for idle CPU for
> > > the generic workqueue based printing. (x86 already does this)
> >
> > How does x86 already do this? What processors do not currently do this?
> >
>
> The default hevaiour on x86 is as below:
> 1) The current CPU (active) is printed.
> 2) There is a hint for idle cpu. This is helpful for me to distingusih whether
> the not printed cpu is in idle or a problem of stacktrace itself (which
> really happed on me).
>
> root@ubuntu:~# echo l > /proc/sysrq-trigger
> [ 34.622117] sysrq: Show backtrace of all active CPUs
> [ 34.622573] NMI backtrace for cpu 0
> [ 34.622576] CPU: 0 PID: 1145 Comm: bash Not tainted 5.16.0+ #120 8a8a684efa076f0b679fc9dbfc6ff35722bf429e
> [ 34.622579] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.15.0-0-g2dd4b9b3f840-prebuilt.qemu.org 04/01/2014
> [ 34.622584] Call Trace:
> [ 34.622588] <TASK>
> [ 34.622589] dump_stack_lvl+0x45/0x59
> [ 34.622598] nmi_cpu_backtrace.cold+0x30/0x76
> [ 34.622600] ? lapic_can_unplug_cpu+0x80/0x80
> [ 34.622605] nmi_trigger_cpumask_backtrace+0x104/0x130
> [ 34.622610] __handle_sysrq.cold+0x43/0x129
> [ 34.622614] write_sysrq_trigger+0x3f/0x50
> [ 34.622618] proc_reg_write+0x55/0xa0
> [ 34.622622] vfs_write+0xe4/0x320
> [ 34.622627] ksys_write+0x68/0xe0
> [ 34.622631] do_syscall_64+0x3b/0xc0
> [ 34.622634] entry_SYSCALL_64_after_hwframe+0x44/0xae
> [ 34.622637] RIP: 0033:0x7f51db009c27
> [ 34.622640] Code: 0d 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b7 0f 1f 00 f3 0f 1e fa 64 8b 04 25 18 00 00 00 85 c0 75 10 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 51 c3 48 83 ec 284
> [ 34.622641] RSP: 002b:00007ffcef29e828 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
> [ 34.622644] RAX: ffffffffffffffda RBX: 0000000000000002 RCX: 00007f51db009c27
> [ 34.622646] RDX: 0000000000000002 RSI: 00005556146896f0 RDI: 0000000000000001
> [ 34.622647] RBP: 00005556146896f0 R08: 000000000000000a R09: 0000000000000000
> [ 34.622648] R10: 00007f51db0a7040 R11: 0000000000000246 R12: 0000000000000002
> [ 34.622649] R13: 00007f51db0e36c0 R14: 00007f51db0e44a0 R15: 00007f51db0e38a0
> [ 34.622657] </TASK>
> [ 34.622658] Sending NMI from CPU 0 to CPUs 1-7:
> [ 34.622676] NMI backtrace for cpu 7
> [ 34.622678] CPU: 7 PID: 1187 Comm: unattended-upgr Not tainted 5.16.0+ #120 8a8a684efa076f0b679fc9dbfc6ff35722bf429e
> [ 34.622681] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.15.0-0-g2dd4b9b3f840-prebuilt.qemu.org 04/01/2014
> [ 34.622682] RIP: 0010:kmem_cache_free+0x27b/0x480
> [ 34.622685] Code: 01 59 01 4c 8d 34 10 48 8b 35 a1 01 59 01 49 c1 ee 0c 49 c1 e6 06 49 01 f6 49 8b 46 08 48 8d 50 ff a8 01 4c 0f 45 f2 49 8b 06 <f6> c4 02 0f 84 20 01 00 00 4d 85 f6 0f8
> [ 34.622687] RSP: 0018:ffffc90000e2bdc0 EFLAGS: 00000202
> [ 34.622689] RAX: 000fffffc0010200 RBX: ffff888009754000 RCX: 0000000000000000
> [ 34.622690] RDX: ffffea000025d400 RSI: ffffea0000000000 RDI: ffff888009754000
> [ 34.622691] RBP: ffffc90000e2be08 R08: 000000080fac04bd R09: 0000000000000000
> [ 34.622692] R10: 0000000000000000 R11: 0000000000000000 R12: ffffffff81436575
> [ 34.622694] R13: ffff888005479100 R14: ffffea000025d400 R15: 0000000000000000
> [ 34.622695] FS: 00007fc9e5b1c740(0000) GS:ffff88807dc00000(0000) knlGS:0000000000000000
> [ 34.622696] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [ 34.622697] CR2: 00007fc9dba14024 CR3: 0000000028f04002 CR4: 0000000000370ee0
> [ 34.622699] Call Trace:
> [ 34.622700] <TASK>
> [ 34.622702] user_path_at_empty+0x45/0x50
> [ 34.622705] vfs_statx+0x74/0x130
> [ 34.622708] __do_sys_newfstatat+0x31/0x70
> [ 34.622710] ? lock_release+0x148/0x430
> [ 34.622714] ? syscall_enter_from_user_mode+0x17/0x60
> [ 34.622716] ? trace_hardirqs_on+0x2b/0xe0
> [ 34.622719] ? syscall_enter_from_user_mode+0x17/0x60
> [ 34.622720] do_syscall_64+0x3b/0xc0
> [ 34.622722] entry_SYSCALL_64_after_hwframe+0x44/0xae
> [ 34.622724] RIP: 0033:0x7fc9e5c260ae
> [ 34.622726] Code: 48 89 f2 b9 00 01 00 00 48 89 fe bf 9c ff ff ff e9 07 00 00 00 0f 1f 80 00 00 00 00 f3 0f 1e fa 41 89 ca b8 06 01 00 00 0f 05 <3d> 00 f0 ff ff 77 0b 31 c0 c3 0f 1f 841
> [ 34.622727] RSP: 002b:00007ffed7182998 EFLAGS: 00000246 ORIG_RAX: 0000000000000106
> [ 34.622729] RAX: ffffffffffffffda RBX: 00000000021f8ab0 RCX: 00007fc9e5c260ae
> [ 34.622730] RDX: 00007ffed71829a0 RSI: 0000000001d90230 RDI: 00000000ffffff9c
> [ 34.622731] RBP: 00007ffed7182ad0 R08: 0000000001d90230 R09: 0000000000000064
> [ 34.622732] R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffed7182ae0
> [ 34.622733] R13: 00007ffed7182ac0 R14: 00007ffed7182b50 R15: 00000000ffffff00
> [ 34.622736] </TASK>
> [ 34.622736] NMI backtrace for cpu 5 skipped: idling at default_idle+0x10/0x20
> [ 34.622743] NMI backtrace for cpu 4 skipped: idling at default_idle+0x10/0x20
> [ 34.622746] NMI backtrace for cpu 6 skipped: idling at default_idle+0x10/0x20
> [ 34.622751] NMI backtrace for cpu 3 skipped: idling at default_idle+0x10/0x20
> [ 34.622756] NMI backtrace for cpu 2 skipped: idling at default_idle+0x10/0x20
> [ 34.622762] NMI backtrace for cpu 1 skipped: idling at default_idle+0x10/0x20
>
>
> > > Now it looks like below:
> > > [ 279.401567] sysrq: Show backtrace of all active CPUs
> > > [ 279.407234] sysrq: CPU5:
> > > [ 279.407505] Call Trace:
> > > [ 279.408789] [<ffffffff8000606c>] dump_backtrace+0x2c/0x3a
> > > [ 279.411698] [<ffffffff800060ac>] show_stack+0x32/0x3e
> > > [ 279.411809] [<ffffffff80542258>] sysrq_handle_showallcpus+0x4c/0xc6
> > > [ 279.411929] [<ffffffff80542f16>] __handle_sysrq+0x106/0x26c
> > > [ 279.412034] [<ffffffff805436a8>] write_sysrq_trigger+0x64/0x74
> > > [ 279.412139] [<ffffffff8029cd48>] proc_reg_write+0x8e/0xe2
> > > [ 279.412252] [<ffffffff8021a8f8>] vfs_write+0x90/0x2be
> > > [ 279.412362] [<ffffffff8021acd2>] ksys_write+0xa6/0xce
> > > [ 279.412467] [<ffffffff8021ad24>] sys_write+0x2a/0x38
> > > [ 279.412689] [<ffffffff80003ff8>] ret_from_syscall+0x0/0x2
> > > [ 279.417173] sysrq: CPU6: backtrace skipped as idling
> > > [ 279.417185] sysrq: CPU4: backtrace skipped as idling
> > > [ 279.417187] sysrq: CPU0: backtrace skipped as idling
> > > [ 279.417181] sysrq: CPU7: backtrace skipped as idling
> > > [ 279.417190] sysrq: CPU1: backtrace skipped as idling
> > > [ 279.417193] sysrq: CPU3: backtrace skipped as idling
> > > [ 279.417219] sysrq: CPU2:
> > > [ 279.419179] Call Trace:
> > > [ 279.419440] [<ffffffff8000606c>] dump_backtrace+0x2c/0x3a
> > > [ 279.419782] [<ffffffff800060ac>] show_stack+0x32/0x3e
> > > [ 279.420015] [<ffffffff80542b30>] showacpu+0x5c/0x96
> > > [ 279.420317] [<ffffffff800ba71c>] flush_smp_call_function_queue+0xd6/0x218
> > > [ 279.420569] [<ffffffff800bb438>] generic_smp_call_function_single_interrupt+0x14/0x1c
> > > [ 279.420798] [<ffffffff800079ae>] handle_IPI+0xaa/0x13a
> > > [ 279.421024] [<ffffffff804dcb92>] riscv_intc_irq+0x56/0x70
> > > [ 279.421274] [<ffffffff80a05b70>] generic_handle_arch_irq+0x6a/0xfa
> > > [ 279.421518] [<ffffffff80004006>] ret_from_exception+0x0/0x10
> > > [ 279.421750] [<ffffffff80096492>] rcu_idle_enter+0x16/0x1e
> > >
> > > Signed-off-by: Changbin Du <changbin.du@gmail.com>
> > > ---
> > > drivers/tty/sysrq.c | 13 +++++++++----
> > > 1 file changed, 9 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c
> > > index bbfd004449b5..34cfdda4aff5 100644
> > > --- a/drivers/tty/sysrq.c
> > > +++ b/drivers/tty/sysrq.c
> > > @@ -232,8 +232,10 @@ static void showacpu(void *dummy)
> > > unsigned long flags;
> > >
> > > /* Idle CPUs have no interesting backtrace. */
> > > - if (idle_cpu(smp_processor_id()))
> > > + if (idle_cpu(smp_processor_id())) {
> > > + pr_info("CPU%d: backtrace skipped as idling\n", smp_processor_id());
> > > return;
> > > + }
> >
> > Why do you need to see the skipped processor? Can't you just infer this
> > from a lack of calltrace on the other cpus? What needs to see this
> > information?
> >
> > >
> > > raw_spin_lock_irqsave(&show_lock, flags);
> > > pr_info("CPU%d:\n", smp_processor_id());
> > > @@ -260,10 +262,13 @@ static void sysrq_handle_showallcpus(int key)
> > >
> > > if (in_hardirq())
> > > regs = get_irq_regs();
> > > - if (regs) {
> > > - pr_info("CPU%d:\n", smp_processor_id());
> > > +
> > > + pr_info("CPU%d:\n", smp_processor_id());
> > > + if (regs)
> > > show_regs(regs);
> > > - }
> > > + else
> > > + show_stack(NULL, NULL, KERN_INFO);
> > > +
> >
> > Why is this change needed as well?
> >
> On the contrary, I wonder why the current cpu is skipped? Isn't it active?
Ok, let's try this and see if people complain :)
_______________________________________________
linux-riscv mailing list
linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv
WARNING: multiple messages have this Message-ID (diff)
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Changbin Du <changbin.du@gmail.com>
Cc: Jiri Slaby <jirislaby@kernel.org>,
Palmer Dabbelt <palmer@dabbelt.com>,
linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org
Subject: Re: [PATCH] sysrq: do not omit current cpu when showing backtrace of all active CPUs
Date: Tue, 26 Apr 2022 13:24:58 +0200 [thread overview]
Message-ID: <YmfWipwuVlAt5Meq@kroah.com> (raw)
In-Reply-To: <20220118003358.6pcowtbds44dntls@mail.google.com>
On Tue, Jan 18, 2022 at 08:33:58AM +0800, Changbin Du wrote:
> Hi, Greg,
> On Mon, Jan 17, 2022 at 04:50:21PM +0100, Greg Kroah-Hartman wrote:
> > On Mon, Jan 17, 2022 at 11:43:00PM +0800, Changbin Du wrote:
> > > The backtrace of current CPU also should be printed as it is active. This
> > > change add stack trace for current CPU and print a hint for idle CPU for
> > > the generic workqueue based printing. (x86 already does this)
> >
> > How does x86 already do this? What processors do not currently do this?
> >
>
> The default hevaiour on x86 is as below:
> 1) The current CPU (active) is printed.
> 2) There is a hint for idle cpu. This is helpful for me to distingusih whether
> the not printed cpu is in idle or a problem of stacktrace itself (which
> really happed on me).
>
> root@ubuntu:~# echo l > /proc/sysrq-trigger
> [ 34.622117] sysrq: Show backtrace of all active CPUs
> [ 34.622573] NMI backtrace for cpu 0
> [ 34.622576] CPU: 0 PID: 1145 Comm: bash Not tainted 5.16.0+ #120 8a8a684efa076f0b679fc9dbfc6ff35722bf429e
> [ 34.622579] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.15.0-0-g2dd4b9b3f840-prebuilt.qemu.org 04/01/2014
> [ 34.622584] Call Trace:
> [ 34.622588] <TASK>
> [ 34.622589] dump_stack_lvl+0x45/0x59
> [ 34.622598] nmi_cpu_backtrace.cold+0x30/0x76
> [ 34.622600] ? lapic_can_unplug_cpu+0x80/0x80
> [ 34.622605] nmi_trigger_cpumask_backtrace+0x104/0x130
> [ 34.622610] __handle_sysrq.cold+0x43/0x129
> [ 34.622614] write_sysrq_trigger+0x3f/0x50
> [ 34.622618] proc_reg_write+0x55/0xa0
> [ 34.622622] vfs_write+0xe4/0x320
> [ 34.622627] ksys_write+0x68/0xe0
> [ 34.622631] do_syscall_64+0x3b/0xc0
> [ 34.622634] entry_SYSCALL_64_after_hwframe+0x44/0xae
> [ 34.622637] RIP: 0033:0x7f51db009c27
> [ 34.622640] Code: 0d 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b7 0f 1f 00 f3 0f 1e fa 64 8b 04 25 18 00 00 00 85 c0 75 10 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 51 c3 48 83 ec 284
> [ 34.622641] RSP: 002b:00007ffcef29e828 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
> [ 34.622644] RAX: ffffffffffffffda RBX: 0000000000000002 RCX: 00007f51db009c27
> [ 34.622646] RDX: 0000000000000002 RSI: 00005556146896f0 RDI: 0000000000000001
> [ 34.622647] RBP: 00005556146896f0 R08: 000000000000000a R09: 0000000000000000
> [ 34.622648] R10: 00007f51db0a7040 R11: 0000000000000246 R12: 0000000000000002
> [ 34.622649] R13: 00007f51db0e36c0 R14: 00007f51db0e44a0 R15: 00007f51db0e38a0
> [ 34.622657] </TASK>
> [ 34.622658] Sending NMI from CPU 0 to CPUs 1-7:
> [ 34.622676] NMI backtrace for cpu 7
> [ 34.622678] CPU: 7 PID: 1187 Comm: unattended-upgr Not tainted 5.16.0+ #120 8a8a684efa076f0b679fc9dbfc6ff35722bf429e
> [ 34.622681] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.15.0-0-g2dd4b9b3f840-prebuilt.qemu.org 04/01/2014
> [ 34.622682] RIP: 0010:kmem_cache_free+0x27b/0x480
> [ 34.622685] Code: 01 59 01 4c 8d 34 10 48 8b 35 a1 01 59 01 49 c1 ee 0c 49 c1 e6 06 49 01 f6 49 8b 46 08 48 8d 50 ff a8 01 4c 0f 45 f2 49 8b 06 <f6> c4 02 0f 84 20 01 00 00 4d 85 f6 0f8
> [ 34.622687] RSP: 0018:ffffc90000e2bdc0 EFLAGS: 00000202
> [ 34.622689] RAX: 000fffffc0010200 RBX: ffff888009754000 RCX: 0000000000000000
> [ 34.622690] RDX: ffffea000025d400 RSI: ffffea0000000000 RDI: ffff888009754000
> [ 34.622691] RBP: ffffc90000e2be08 R08: 000000080fac04bd R09: 0000000000000000
> [ 34.622692] R10: 0000000000000000 R11: 0000000000000000 R12: ffffffff81436575
> [ 34.622694] R13: ffff888005479100 R14: ffffea000025d400 R15: 0000000000000000
> [ 34.622695] FS: 00007fc9e5b1c740(0000) GS:ffff88807dc00000(0000) knlGS:0000000000000000
> [ 34.622696] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [ 34.622697] CR2: 00007fc9dba14024 CR3: 0000000028f04002 CR4: 0000000000370ee0
> [ 34.622699] Call Trace:
> [ 34.622700] <TASK>
> [ 34.622702] user_path_at_empty+0x45/0x50
> [ 34.622705] vfs_statx+0x74/0x130
> [ 34.622708] __do_sys_newfstatat+0x31/0x70
> [ 34.622710] ? lock_release+0x148/0x430
> [ 34.622714] ? syscall_enter_from_user_mode+0x17/0x60
> [ 34.622716] ? trace_hardirqs_on+0x2b/0xe0
> [ 34.622719] ? syscall_enter_from_user_mode+0x17/0x60
> [ 34.622720] do_syscall_64+0x3b/0xc0
> [ 34.622722] entry_SYSCALL_64_after_hwframe+0x44/0xae
> [ 34.622724] RIP: 0033:0x7fc9e5c260ae
> [ 34.622726] Code: 48 89 f2 b9 00 01 00 00 48 89 fe bf 9c ff ff ff e9 07 00 00 00 0f 1f 80 00 00 00 00 f3 0f 1e fa 41 89 ca b8 06 01 00 00 0f 05 <3d> 00 f0 ff ff 77 0b 31 c0 c3 0f 1f 841
> [ 34.622727] RSP: 002b:00007ffed7182998 EFLAGS: 00000246 ORIG_RAX: 0000000000000106
> [ 34.622729] RAX: ffffffffffffffda RBX: 00000000021f8ab0 RCX: 00007fc9e5c260ae
> [ 34.622730] RDX: 00007ffed71829a0 RSI: 0000000001d90230 RDI: 00000000ffffff9c
> [ 34.622731] RBP: 00007ffed7182ad0 R08: 0000000001d90230 R09: 0000000000000064
> [ 34.622732] R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffed7182ae0
> [ 34.622733] R13: 00007ffed7182ac0 R14: 00007ffed7182b50 R15: 00000000ffffff00
> [ 34.622736] </TASK>
> [ 34.622736] NMI backtrace for cpu 5 skipped: idling at default_idle+0x10/0x20
> [ 34.622743] NMI backtrace for cpu 4 skipped: idling at default_idle+0x10/0x20
> [ 34.622746] NMI backtrace for cpu 6 skipped: idling at default_idle+0x10/0x20
> [ 34.622751] NMI backtrace for cpu 3 skipped: idling at default_idle+0x10/0x20
> [ 34.622756] NMI backtrace for cpu 2 skipped: idling at default_idle+0x10/0x20
> [ 34.622762] NMI backtrace for cpu 1 skipped: idling at default_idle+0x10/0x20
>
>
> > > Now it looks like below:
> > > [ 279.401567] sysrq: Show backtrace of all active CPUs
> > > [ 279.407234] sysrq: CPU5:
> > > [ 279.407505] Call Trace:
> > > [ 279.408789] [<ffffffff8000606c>] dump_backtrace+0x2c/0x3a
> > > [ 279.411698] [<ffffffff800060ac>] show_stack+0x32/0x3e
> > > [ 279.411809] [<ffffffff80542258>] sysrq_handle_showallcpus+0x4c/0xc6
> > > [ 279.411929] [<ffffffff80542f16>] __handle_sysrq+0x106/0x26c
> > > [ 279.412034] [<ffffffff805436a8>] write_sysrq_trigger+0x64/0x74
> > > [ 279.412139] [<ffffffff8029cd48>] proc_reg_write+0x8e/0xe2
> > > [ 279.412252] [<ffffffff8021a8f8>] vfs_write+0x90/0x2be
> > > [ 279.412362] [<ffffffff8021acd2>] ksys_write+0xa6/0xce
> > > [ 279.412467] [<ffffffff8021ad24>] sys_write+0x2a/0x38
> > > [ 279.412689] [<ffffffff80003ff8>] ret_from_syscall+0x0/0x2
> > > [ 279.417173] sysrq: CPU6: backtrace skipped as idling
> > > [ 279.417185] sysrq: CPU4: backtrace skipped as idling
> > > [ 279.417187] sysrq: CPU0: backtrace skipped as idling
> > > [ 279.417181] sysrq: CPU7: backtrace skipped as idling
> > > [ 279.417190] sysrq: CPU1: backtrace skipped as idling
> > > [ 279.417193] sysrq: CPU3: backtrace skipped as idling
> > > [ 279.417219] sysrq: CPU2:
> > > [ 279.419179] Call Trace:
> > > [ 279.419440] [<ffffffff8000606c>] dump_backtrace+0x2c/0x3a
> > > [ 279.419782] [<ffffffff800060ac>] show_stack+0x32/0x3e
> > > [ 279.420015] [<ffffffff80542b30>] showacpu+0x5c/0x96
> > > [ 279.420317] [<ffffffff800ba71c>] flush_smp_call_function_queue+0xd6/0x218
> > > [ 279.420569] [<ffffffff800bb438>] generic_smp_call_function_single_interrupt+0x14/0x1c
> > > [ 279.420798] [<ffffffff800079ae>] handle_IPI+0xaa/0x13a
> > > [ 279.421024] [<ffffffff804dcb92>] riscv_intc_irq+0x56/0x70
> > > [ 279.421274] [<ffffffff80a05b70>] generic_handle_arch_irq+0x6a/0xfa
> > > [ 279.421518] [<ffffffff80004006>] ret_from_exception+0x0/0x10
> > > [ 279.421750] [<ffffffff80096492>] rcu_idle_enter+0x16/0x1e
> > >
> > > Signed-off-by: Changbin Du <changbin.du@gmail.com>
> > > ---
> > > drivers/tty/sysrq.c | 13 +++++++++----
> > > 1 file changed, 9 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c
> > > index bbfd004449b5..34cfdda4aff5 100644
> > > --- a/drivers/tty/sysrq.c
> > > +++ b/drivers/tty/sysrq.c
> > > @@ -232,8 +232,10 @@ static void showacpu(void *dummy)
> > > unsigned long flags;
> > >
> > > /* Idle CPUs have no interesting backtrace. */
> > > - if (idle_cpu(smp_processor_id()))
> > > + if (idle_cpu(smp_processor_id())) {
> > > + pr_info("CPU%d: backtrace skipped as idling\n", smp_processor_id());
> > > return;
> > > + }
> >
> > Why do you need to see the skipped processor? Can't you just infer this
> > from a lack of calltrace on the other cpus? What needs to see this
> > information?
> >
> > >
> > > raw_spin_lock_irqsave(&show_lock, flags);
> > > pr_info("CPU%d:\n", smp_processor_id());
> > > @@ -260,10 +262,13 @@ static void sysrq_handle_showallcpus(int key)
> > >
> > > if (in_hardirq())
> > > regs = get_irq_regs();
> > > - if (regs) {
> > > - pr_info("CPU%d:\n", smp_processor_id());
> > > +
> > > + pr_info("CPU%d:\n", smp_processor_id());
> > > + if (regs)
> > > show_regs(regs);
> > > - }
> > > + else
> > > + show_stack(NULL, NULL, KERN_INFO);
> > > +
> >
> > Why is this change needed as well?
> >
> On the contrary, I wonder why the current cpu is skipped? Isn't it active?
Ok, let's try this and see if people complain :)
next prev parent reply other threads:[~2022-04-26 11:25 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-17 15:43 [PATCH] sysrq: do not omit current cpu when showing backtrace of all active CPUs Changbin Du
2022-01-17 15:43 ` Changbin Du
2022-01-17 15:50 ` Greg Kroah-Hartman
2022-01-17 15:50 ` Greg Kroah-Hartman
2022-01-18 0:33 ` Changbin Du
2022-01-18 0:33 ` Changbin Du
2022-04-26 11:24 ` Greg Kroah-Hartman [this message]
2022-04-26 11:24 ` Greg Kroah-Hartman
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=YmfWipwuVlAt5Meq@kroah.com \
--to=gregkh@linuxfoundation.org \
--cc=changbin.du@gmail.com \
--cc=jirislaby@kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-riscv@lists.infradead.org \
--cc=palmer@dabbelt.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.