kernel/linux.git/drivers/tty/sysrq.c, branch v5.10.257

tty/sysrq: replace smp_processor_id() with get_cpu()

2023-11-28T16:54:56+00:00

commit dd976a97d15b47656991e185a94ef42a0fa5cfd4 upstream. 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. Enable preemption back after calling schedule_work() to make sure that the work gets scheduled on all cores other than the current core. We want to avoid a scenario where current core's stack trace is printed multiple times and one core's stack trace isn't printed because of scheduling of current task. 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: jirislaby@kernel.org Cc: stable@vger.kernel.org Fixes: 47cab6a722d4 ("debug lockups: Improve lockup detection, fix generic arch fallback") Signed-off-by: Muhammad Usama Anjum Link: https://lore.kernel.org/r/20231009162021.3607632-1-usama.anjum@collabora.com Signed-off-by: Greg Kroah-Hartman Signed-off-by: Greg Kroah-Hartman

sysrq: do not omit current cpu when showing backtrace of all active CPUs

2022-06-14T16:32:42+00:00

[ Upstream commit 5390e7f46b9d5546d45a83e6463bc656678b1d0e ] 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) Now it looks like below: [ 279.401567] sysrq: Show backtrace of all active CPUs [ 279.407234] sysrq: CPU5: [ 279.407505] Call Trace: [ 279.408789] [] dump_backtrace+0x2c/0x3a [ 279.411698] [] show_stack+0x32/0x3e [ 279.411809] [] sysrq_handle_showallcpus+0x4c/0xc6 [ 279.411929] [] __handle_sysrq+0x106/0x26c [ 279.412034] [] write_sysrq_trigger+0x64/0x74 [ 279.412139] [] proc_reg_write+0x8e/0xe2 [ 279.412252] [] vfs_write+0x90/0x2be [ 279.412362] [] ksys_write+0xa6/0xce [ 279.412467] [] sys_write+0x2a/0x38 [ 279.412689] [] 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] [] dump_backtrace+0x2c/0x3a [ 279.419782] [] show_stack+0x32/0x3e [ 279.420015] [] showacpu+0x5c/0x96 [ 279.420317] [] flush_smp_call_function_queue+0xd6/0x218 [ 279.420569] [] generic_smp_call_function_single_interrupt+0x14/0x1c [ 279.420798] [] handle_IPI+0xaa/0x13a [ 279.421024] [] riscv_intc_irq+0x56/0x70 [ 279.421274] [] generic_handle_arch_irq+0x6a/0xfa [ 279.421518] [] ret_from_exception+0x0/0x10 [ 279.421750] [] rcu_idle_enter+0x16/0x1e Signed-off-by: Changbin Du Link: https://lore.kernel.org/r/20220117154300.2808-1-changbin.du@gmail.com Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin

tty/sysrq: Extend the sysrq_key_table to cover capital letters

2020-10-02T12:56:06+00:00

All slots in sysrq_key_table[] are either used, reserved or at least commented with their intended use. This patch adds capital letter versions available, which means adding 26 more entries. For already existing SysRq operations the user presses Alt-SysRq-, and for the newly added ones Alt-Shift-SysRq-. Signed-off-by: Andrzej Pietrasiewicz Acked-by: Daniel Vetter Link: https://lore.kernel.org/r/20200818112825.6445-2-andrzej.p@collabora.com Signed-off-by: Greg Kroah-Hartman

tty/sysrq: emergency_thaw_all does not depend on CONFIG_BLOCK

2020-06-24T15:16:02+00:00

We can also thaw non-block file systems. Remove the CONFIG_BLOCK in sysrq.c after making the prototype available unconditionally. Signed-off-by: Christoph Hellwig Reviewed-by: Bart Van Assche Reviewed-by: Greg Kroah-Hartman Signed-off-by: Jens Axboe

kernel: rename show_stack_loglvl() => show_stack()

2020-06-09T16:39:13+00:00

Now the last users of show_stack() got converted to use an explicit log level, show_stack_loglvl() can drop it's redundant suffix and become once again well known show_stack(). Signed-off-by: Dmitry Safonov Signed-off-by: Andrew Morton Link: http://lkml.kernel.org/r/20200418201944.482088-51-dima@arista.com Signed-off-by: Linus Torvalds

sysrq: use show_stack_loglvl()

2020-06-09T16:39:12+00:00

Show the stack trace on a CPU with the same log level as "CPU%d" header. Signed-off-by: Dmitry Safonov Signed-off-by: Andrew Morton Cc: Greg Kroah-Hartman Cc: Jiri Slaby Link: http://lkml.kernel.org/r/20200418201944.482088-45-dima@arista.com Signed-off-by: Linus Torvalds

tty/sysrq: constify the the sysrq_key_op(s)

2020-05-15T12:53:19+00:00

All the users threat them as immutable - annotate them as such. Cc: Greg Kroah-Hartman Cc: Jiri Slaby Cc: linux-kernel@vger.kernel.org Signed-off-by: Emil Velikov Link: https://lore.kernel.org/r/20200513214351.2138580-3-emil.l.velikov@gmail.com Signed-off-by: Greg Kroah-Hartman

tty/sysrq: constify the sysrq API

2020-05-15T12:53:19+00:00

The user is not supposed to thinker with the underlying sysrq_key_op. Make that explicit by adding a handful of const notations. Cc: Greg Kroah-Hartman Cc: Jiri Slaby Cc: linux-kernel@vger.kernel.org Signed-off-by: Emil Velikov Link: https://lore.kernel.org/r/20200513214351.2138580-2-emil.l.velikov@gmail.com Signed-off-by: Greg Kroah-Hartman

tty/sysrq: alpha: export and use __sysrq_get_key_op()

2020-05-15T12:53:18+00:00

Export a pointer to the sysrq_get_key_op(). This way we can cleanly unregister it, instead of the current solutions of modifuing it inplace. Since __sysrq_get_key_op() is no longer used externally, let's make it a static function. This patch will allow us to limit access to each and every sysrq op and constify the sysrq handling. Cc: Greg Kroah-Hartman Cc: Jiri Slaby Cc: linux-kernel@vger.kernel.org Cc: Richard Henderson Cc: Ivan Kokshaysky Cc: Matt Turner Cc: linux-alpha@vger.kernel.org Signed-off-by: Emil Velikov Link: https://lore.kernel.org/r/20200513214351.2138580-1-emil.l.velikov@gmail.com Signed-off-by: Greg Kroah-Hartman

tty/sysrq: Export sysrq_mask(), sysrq_toggle_support()

2020-04-20T17:37:42+00:00

Build fix for serial_core being module: ERROR: modpost: "sysrq_toggle_support" [drivers/tty/serial/serial_core.ko] undefined! ERROR: modpost: "sysrq_mask" [drivers/tty/serial/serial_core.ko] undefined! Fixes: eaee41727e6d ("sysctl/sysrq: Remove __sysrq_enabled copy") Cc: Jiri Slaby Reported-by: "kernelci.org bot" Reported-by: Michael Ellerman Reported-by: Stephen Rothwell Signed-off-by: Dmitry Safonov Link: https://lore.kernel.org/r/20200420172317.599611-1-dima@arista.com Signed-off-by: Greg Kroah-Hartman