From 2fb47220593d4b9191914b7d97095628d5b0f940 Mon Sep 17 00:00:00 2001 From: Changbin Du Date: Mon, 17 Jan 2022 23:43:00 +0800 Subject: [PATCH] sysrq: do not omit current cpu when showing backtrace of all active CPUs [ 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 --- 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 bbfd004449b5b..34cfdda4aff5d 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; + } 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); + schedule_work(&sysrq_showallcpus); } }