Hello Pingfan Liu,
The patch 55f2503c3b69: "PM / reboot: Eliminate race between reboot
and suspend" from Jul 31, 2018, leads to the following static checker
warning:
kernel/power/main.c:27 lock_system_sleep()
warn: called with lock held. '&system_transition_mutex'
kernel/reboot.c
345
346 mutex_lock(&system_transition_mutex);
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
The patch changed the code to take this lock.
347 switch (cmd) {
348 case LINUX_REBOOT_CMD_RESTART:
349 kernel_restart(NULL);
350 break;
351
352 case LINUX_REBOOT_CMD_CAD_ON:
353 C_A_D = 1;
354 break;
355
356 case LINUX_REBOOT_CMD_CAD_OFF:
357 C_A_D = 0;
358 break;
359
360 case LINUX_REBOOT_CMD_HALT:
361 kernel_halt();
362 do_exit(0);
363 panic("cannot halt");
364
365 case LINUX_REBOOT_CMD_POWER_OFF:
366 kernel_power_off();
367 do_exit(0);
368 break;
369
370 case LINUX_REBOOT_CMD_RESTART2:
371 ret = strncpy_from_user(&buffer[0], arg, sizeof(buffer) - 1);
372 if (ret < 0) {
373 ret = -EFAULT;
374 break;
375 }
376 buffer[sizeof(buffer) - 1] = '\0';
377
378 kernel_restart(buffer);
379 break;
380
381 #ifdef CONFIG_KEXEC_CORE
382 case LINUX_REBOOT_CMD_KEXEC:
383 ret = kernel_kexec();
^^^^^^^^^^^^^^^^^^^^
Called with lock held.
384 break;
385 #endif
But kernel_kexec() also tries to take the &system_transition_mutex so
it will dead lock.
kernel/kexec_core.c
1125 int kernel_kexec(void)
1126 {
1127 int error = 0;
1128
1129 if (!mutex_trylock(&kexec_mutex))
1130 return -EBUSY;
1131 if (!kexec_image) {
1132 error = -EINVAL;
1133 goto Unlock;
1134 }
1135
1136 #ifdef CONFIG_KEXEC_JUMP
1137 if (kexec_image->preserve_context) {
1138 lock_system_sleep();
^^^^^^^^^^^^^^^^^^^
Here.
1139 pm_prepare_console();
1140 error = freeze_processes();
1141 if (error) {
1142 error = -EBUSY;
1143 goto Restore_console;
1144 }
1145 suspend_console();
1146 error = dpm_suspend_start(PMSG_FREEZE);
1147 if (error)
1148 goto Resume_console;
1149 /* At this point, dpm_suspend_start() has been called,
1150 * but *not* dpm_suspend_end(). We *must* call
1151 * dpm_suspend_end() now. Otherwise, drivers for
1152 * some devices (e.g. interrupt controllers) become
1153 * desynchronized with the actual state of the
1154 * hardware at resume time, and evil weirdness ensues.
1155 */
1156 error = dpm_suspend_end(PMSG_FREEZE);
1157 if (error)
1158 goto Resume_devices;
1159 error = suspend_disable_secondary_cpus();
1160 if (error)
regards,
dan carpenter
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