I am running freertos on 2 cpus - at one customer site I see occasional errors such as the following, sometimes with TG0 and sometimes with TG1, and every so often the board even locks up (but that's w/o any errors whatsoever). The stack pointer printed often points to a "Double Exception".
I was unable to find a clear explanation of the timer group 1 and group 0 watchdog resets. As best I could figure out it when TG1 fires it means that FreeRTOS task switching was blocked for a long time (how long?), which would prevent important interrupts from firing. This only happens at one site where the customer has many device on modbus. But not reading from some of the modbus devices didn't help matters.
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[2018-11-07T23:55:58.879] [ALL] USB - ���������������������;�IՁMeditatiol Error����� 0 panic'ed (D/uble epception)
[2018-11-07T23:55:58.882] [ALL] USB - Register dump:
[2018-11-07T23:55:59.876] [ALL] USB - PC : 0x400d216a PS : 0x00060836 A0 : ets Jun 8 2016 00:22:57
[2018-11-07T23:55:59.877] [ALL] USB -
[2018-11-07T23:55:59.882] [ALL] USB - rst:0x7 (TG0WDT_SYS_RESET),boot:0x17 (SPI_FAST_FLASH_BOOT)
[2018-11-07T23:55:59.885] [ALL] USB - configsip: 0, SPIWP:0xee
[2018-11-07T23:55:59.890] [ALL] USB - clk_drv:0x00,q_drv:0x00,d_drv:0x00,cs0_drv:0x00,hd_drv:0x00,wp_drv:0x00
[2018-11-07T23:55:59.892] [ALL] USB - mode:DIO, clock div:2
[2018-11-07T23:55:59.932] [ALL] USB - load:0x3fff0p���f���怘�����x��xx�xx������f���f��x怘�����x������f������������x~f��������怘�����x������f��������f怘�f��`��f����fx`����`��~�x�~�������~�f�������~f~ff�xfxf~f��f�~�������f���W (74) boot: PRO CPU has been reset by WDT.
[2018-11-07T23:55:59.939] [ALL] USB - W (74) boot: WDT reset info: PRO CPU PC=0x400803c3 (waiti mode)
[2018-11-07T23:55:59.944] [ALL] USB - W (76) boot: WDT reset info: APP CPU PC=0x40084b63