* [PATCH v2 RESEND] tty/sysrq: replace smp_processor_id() with get_cpu()
@ 2023-08-22 9:01 Muhammad Usama Anjum
2023-08-22 9:15 ` Greg Kroah-Hartman
0 siblings, 1 reply; 3+ messages in thread
From: Muhammad Usama Anjum @ 2023-08-22 9:01 UTC (permalink / raw)
To: Greg Kroah-Hartman, Jiri Slaby, Ingo Molnar
Cc: Muhammad Usama Anjum, kernel, stable, linux-kernel, linux-serial
The smp_processor_id() shouldn't be called from preemptible code.
Instead use get_cpu() and put_cpu() which disables preemption in
addition to getting the processor id. This fixes the following bug:
[ 119.143590] sysrq: Show backtrace of all active CPUs
[ 119.143902] BUG: using smp_processor_id() in preemptible [00000000] code: bash/873
[ 119.144586] caller is debug_smp_processor_id+0x20/0x30
[ 119.144827] CPU: 6 PID: 873 Comm: bash Not tainted 5.10.124-dirty #3
[ 119.144861] Hardware name: QEMU QEMU Virtual Machine, BIOS 2023.05-1 07/22/2023
[ 119.145053] Call trace:
[ 119.145093] dump_backtrace+0x0/0x1a0
[ 119.145122] show_stack+0x18/0x70
[ 119.145141] dump_stack+0xc4/0x11c
[ 119.145159] check_preemption_disabled+0x100/0x110
[ 119.145175] debug_smp_processor_id+0x20/0x30
[ 119.145195] sysrq_handle_showallcpus+0x20/0xc0
[ 119.145211] __handle_sysrq+0x8c/0x1a0
[ 119.145227] write_sysrq_trigger+0x94/0x12c
[ 119.145247] proc_reg_write+0xa8/0xe4
[ 119.145266] vfs_write+0xec/0x280
[ 119.145282] ksys_write+0x6c/0x100
[ 119.145298] __arm64_sys_write+0x20/0x30
[ 119.145315] el0_svc_common.constprop.0+0x78/0x1e4
[ 119.145332] do_el0_svc+0x24/0x8c
[ 119.145348] el0_svc+0x10/0x20
[ 119.145364] el0_sync_handler+0x134/0x140
[ 119.145381] el0_sync+0x180/0x1c0
Cc: stable@vger.kernel.org
Fixes: 47cab6a722d4 ("debug lockups: Improve lockup detection, fix generic arch fallback")
Signed-off-by: Muhammad Usama Anjum <usama.anjum@collabora.com>
---
Changes since v1:
- Add "Cc: stable@vger.kernel.org" tag
---
drivers/tty/sysrq.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c
index 23198e3f1461a..6b4a28bcf2f5f 100644
--- a/drivers/tty/sysrq.c
+++ b/drivers/tty/sysrq.c
@@ -262,13 +262,14 @@ static void sysrq_handle_showallcpus(u8 key)
if (in_hardirq())
regs = get_irq_regs();
- pr_info("CPU%d:\n", smp_processor_id());
+ pr_info("CPU%d:\n", get_cpu());
if (regs)
show_regs(regs);
else
show_stack(NULL, NULL, KERN_INFO);
schedule_work(&sysrq_showallcpus);
+ put_cpu();
}
}
--
2.40.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH v2 RESEND] tty/sysrq: replace smp_processor_id() with get_cpu()
2023-08-22 9:01 [PATCH v2 RESEND] tty/sysrq: replace smp_processor_id() with get_cpu() Muhammad Usama Anjum
@ 2023-08-22 9:15 ` Greg Kroah-Hartman
2023-08-22 10:27 ` Muhammad Usama Anjum
0 siblings, 1 reply; 3+ messages in thread
From: Greg Kroah-Hartman @ 2023-08-22 9:15 UTC (permalink / raw)
To: Muhammad Usama Anjum
Cc: Jiri Slaby, Ingo Molnar, kernel, stable, linux-kernel,
linux-serial
On Tue, Aug 22, 2023 at 02:01:11PM +0500, Muhammad Usama Anjum wrote:
> The smp_processor_id() shouldn't be called from preemptible code.
> Instead use get_cpu() and put_cpu() which disables preemption in
> addition to getting the processor id. This fixes the following bug:
>
> [ 119.143590] sysrq: Show backtrace of all active CPUs
> [ 119.143902] BUG: using smp_processor_id() in preemptible [00000000] code: bash/873
> [ 119.144586] caller is debug_smp_processor_id+0x20/0x30
> [ 119.144827] CPU: 6 PID: 873 Comm: bash Not tainted 5.10.124-dirty #3
> [ 119.144861] Hardware name: QEMU QEMU Virtual Machine, BIOS 2023.05-1 07/22/2023
> [ 119.145053] Call trace:
> [ 119.145093] dump_backtrace+0x0/0x1a0
> [ 119.145122] show_stack+0x18/0x70
> [ 119.145141] dump_stack+0xc4/0x11c
> [ 119.145159] check_preemption_disabled+0x100/0x110
> [ 119.145175] debug_smp_processor_id+0x20/0x30
> [ 119.145195] sysrq_handle_showallcpus+0x20/0xc0
> [ 119.145211] __handle_sysrq+0x8c/0x1a0
> [ 119.145227] write_sysrq_trigger+0x94/0x12c
> [ 119.145247] proc_reg_write+0xa8/0xe4
> [ 119.145266] vfs_write+0xec/0x280
> [ 119.145282] ksys_write+0x6c/0x100
> [ 119.145298] __arm64_sys_write+0x20/0x30
> [ 119.145315] el0_svc_common.constprop.0+0x78/0x1e4
> [ 119.145332] do_el0_svc+0x24/0x8c
> [ 119.145348] el0_svc+0x10/0x20
> [ 119.145364] el0_sync_handler+0x134/0x140
> [ 119.145381] el0_sync+0x180/0x1c0
>
> Cc: stable@vger.kernel.org
> Fixes: 47cab6a722d4 ("debug lockups: Improve lockup detection, fix generic arch fallback")
> Signed-off-by: Muhammad Usama Anjum <usama.anjum@collabora.com>
> ---
> Changes since v1:
> - Add "Cc: stable@vger.kernel.org" tag
> ---
This is not a resend, it is a new version, v3. Otherwise I would be
confused with the original v2 which is different than this one...
thanks,
greg k-h
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH v2 RESEND] tty/sysrq: replace smp_processor_id() with get_cpu()
2023-08-22 9:15 ` Greg Kroah-Hartman
@ 2023-08-22 10:27 ` Muhammad Usama Anjum
0 siblings, 0 replies; 3+ messages in thread
From: Muhammad Usama Anjum @ 2023-08-22 10:27 UTC (permalink / raw)
To: Greg Kroah-Hartman
Cc: Muhammad Usama Anjum, Jiri Slaby, Ingo Molnar, kernel, stable,
linux-kernel, linux-serial
On 8/22/23 2:15 PM, Greg Kroah-Hartman wrote:
> On Tue, Aug 22, 2023 at 02:01:11PM +0500, Muhammad Usama Anjum wrote:
>> The smp_processor_id() shouldn't be called from preemptible code.
>> Instead use get_cpu() and put_cpu() which disables preemption in
>> addition to getting the processor id. This fixes the following bug:
>>
>> [ 119.143590] sysrq: Show backtrace of all active CPUs
>> [ 119.143902] BUG: using smp_processor_id() in preemptible [00000000] code: bash/873
>> [ 119.144586] caller is debug_smp_processor_id+0x20/0x30
>> [ 119.144827] CPU: 6 PID: 873 Comm: bash Not tainted 5.10.124-dirty #3
>> [ 119.144861] Hardware name: QEMU QEMU Virtual Machine, BIOS 2023.05-1 07/22/2023
>> [ 119.145053] Call trace:
>> [ 119.145093] dump_backtrace+0x0/0x1a0
>> [ 119.145122] show_stack+0x18/0x70
>> [ 119.145141] dump_stack+0xc4/0x11c
>> [ 119.145159] check_preemption_disabled+0x100/0x110
>> [ 119.145175] debug_smp_processor_id+0x20/0x30
>> [ 119.145195] sysrq_handle_showallcpus+0x20/0xc0
>> [ 119.145211] __handle_sysrq+0x8c/0x1a0
>> [ 119.145227] write_sysrq_trigger+0x94/0x12c
>> [ 119.145247] proc_reg_write+0xa8/0xe4
>> [ 119.145266] vfs_write+0xec/0x280
>> [ 119.145282] ksys_write+0x6c/0x100
>> [ 119.145298] __arm64_sys_write+0x20/0x30
>> [ 119.145315] el0_svc_common.constprop.0+0x78/0x1e4
>> [ 119.145332] do_el0_svc+0x24/0x8c
>> [ 119.145348] el0_svc+0x10/0x20
>> [ 119.145364] el0_sync_handler+0x134/0x140
>> [ 119.145381] el0_sync+0x180/0x1c0
>>
>> Cc: stable@vger.kernel.org
>> Fixes: 47cab6a722d4 ("debug lockups: Improve lockup detection, fix generic arch fallback")
>> Signed-off-by: Muhammad Usama Anjum <usama.anjum@collabora.com>
>> ---
>> Changes since v1:
>> - Add "Cc: stable@vger.kernel.org" tag
>> ---
>
> This is not a resend, it is a new version, v3. Otherwise I would be
> confused with the original v2 which is different than this one...
Sorry, didn't relaize this. I've sent this as v3:
https://lore.kernel.org/all/20230822102606.2821311-1-usama.anjum@collabora.com
>
> thanks,
>
> greg k-h
--
BR,
Muhammad Usama Anjum
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2023-08-22 10:27 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2023-08-22 9:01 [PATCH v2 RESEND] tty/sysrq: replace smp_processor_id() with get_cpu() Muhammad Usama Anjum
2023-08-22 9:15 ` Greg Kroah-Hartman
2023-08-22 10:27 ` Muhammad Usama Anjum
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox