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When kernel configuration SMP,PREEMPT and DEBUG_PREEMPT are enabled, echo 1 >/proc/sys/kernel/sysrq echo p >/proc/sysrq-trigger kernel will print call trace as below: sysrq: SysRq : Show Regs BUG: using __this_cpu_read() in preemptible [00000000] code: sh/435 caller is __this_cpu_preempt_check+0x18/0x20 Call trace: [<ffffff8008088e80>] dump_backtrace+0x0/0x1d0 [<ffffff8008089074>] show_stack+0x24/0x30 [<ffffff8008447970>] dump_stack+0x90/0xb0 [<ffffff8008463950>] check_preemption_disabled+0x100/0x108 [<ffffff8008463998>] __this_cpu_preempt_check+0x18/0x20 [<ffffff80084c9194>] sysrq_handle_showregs+0x1c/0x40 [<ffffff80084c9c7c>] __handle_sysrq+0x12c/0x1a0 [<ffffff80084ca140>] write_sysrq_trigger+0x60/0x70 [<ffffff8008251e00>] proc_reg_write+0x90/0xd0 [<ffffff80081f1788>] __vfs_write+0x48/0x90 [<ffffff80081f241c>] vfs_write+0xa4/0x190 [<ffffff80081f3354>] SyS_write+0x54/0xb0 [<ffffff80080833f0>] el0_svc_naked+0x24/0x28 This can be seen on a common board like an r-pi3. This happens because when echo p >/proc/sysrq-trigger, get_irq_regs() is called outside of IRQ context, if preemption is enabled in this situation,kernel will print the call trace. Since many prior discussions on the mailing lists have made it clear that get_irq_regs either just returns NULL or stale data when used outside of IRQ context,we simply avoid calling it outside of IRQ context. Signed-off-by: Jibin Xu <jibin.xu@windriver.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
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| .. | ||
| hvc | ||
| ipwireless | ||
| serdev | ||
| serial | ||
| vt | ||
| amiserial.c | ||
| bfin_jtag_comm.c | ||
| cyclades.c | ||
| ehv_bytechan.c | ||
| goldfish.c | ||
| isicom.c | ||
| Kconfig | ||
| Makefile | ||
| metag_da.c | ||
| mips_ejtag_fdc.c | ||
| moxa.c | ||
| moxa.h | ||
| mxser.c | ||
| mxser.h | ||
| n_gsm.c | ||
| n_hdlc.c | ||
| n_null.c | ||
| n_r3964.c | ||
| n_tracerouter.c | ||
| n_tracesink.c | ||
| n_tracesink.h | ||
| n_tty.c | ||
| nozomi.c | ||
| pty.c | ||
| rocket.c | ||
| rocket.h | ||
| rocket_int.h | ||
| synclink.c | ||
| synclink_gt.c | ||
| synclinkmp.c | ||
| sysrq.c | ||
| tty_audit.c | ||
| tty_baudrate.c | ||
| tty_buffer.c | ||
| tty_io.c | ||
| tty_ioctl.c | ||
| tty_jobctrl.c | ||
| tty_ldisc.c | ||
| tty_ldsem.c | ||
| tty_mutex.c | ||
| tty_port.c | ||
| vcc.c | ||