Using preferences in esp32 ISR - esp32

Question

I am trying to store the value in esp32 using preferences library when an interrupt is triggered.
Guru Meditation Error: Core 1 panic'ed (Interrupt wdt timeout on CPU1)
Core 1 register dump:
PC : 0x4008867a PS : 0x00060034 A0 : 0x80087a9b A1 : 0x3ffbe860
A2 : 0x3ffb7e0c A3 : 0x3ffb8074 A4 : 0x00000001 A5 : 0x00000001
A6 : 0x00060023 A7 : 0x00000000 A8 : 0x3ffb8074 A9 : 0x3ffb8074
A10 : 0x00000001 A11 : 0x00000001 A12 : 0x00000020 A13 : 0x0000ff00
A14 : 0x00ff0000 A15 : 0xff000000 SAR : 0x0000001e EXCCAUSE: 0x00000006
EXCVADDR: 0x00000000 LBEG : 0x4000c2e0 LEND : 0x4000c2f6 LCOUNT : 0xffffffff
Core 1 was running in ISR context:
EPC1 : 0x40085d07 EPC2 : 0x00000000 EPC3 : 0x00000000 EPC4 : 0x4008867a
ELF file SHA256: 0000000000000000
Backtrace: 0x4008867a:0x3ffbe860 0x40087a98:0x3ffbe880 0x400860cf:0x3ffbe8a0 0x400e2f42:0x3ffbe8e0 0x400e300a:0x3ffbe900 0x40083cad:0x3ffbe920 0x400840c4:0x3ffbe940 0x400e7b01:0x3ffbe990 0x400e5f66:0x3ffbe9b0 0x400e629e:0x3ffbe9d0 0x400e5a92:0x3ffbea50 0x400e4a77:0x3ffbeac0 0x400e4e55:0x3ffbeb10 0x400d1fa4:0x3ffbeb30 0x40080ecd:0x3ffbeb50 0x40080f19:0x3ffbeb70 0x40083969:0x3ffbeb90 0x40081b46:0x3ffb1e00 0x400826ef:0x3ffb1e20 0x40081183:0x3ffb1e40 0x400811a7:0x3ffb1e60 0x400d1cb7:0x3ffb1e80 0x400d1c85:0x3ffb1ea0 0x400d1c30:0x3ffb1ec0 0x400ebb35:0x3ffb1ee0 0x400ebbfe:0x3ffb1f00 0x400d1795:0x3ffb1f30 0x400d18da:0x3ffb1f70 0x400d1b47:0x3ffb1f90 0x400d33e9:0x3ffb1fb0 0x40086295:0x3ffb1fd0
Core 0 register dump:
PC : 0x40086729 PS : 0x00060034 A0 : 0x80086bd6 A1 : 0x3ffbc020
A2 : 0x3ffbdf74 A3 : 0xb33fffff A4 : 0x00060023 A5 : 0x003fffff
A6 : 0x00060021 A7 : 0x00000000 A8 : 0x0000abab A9 : 0x0000cdcd
A10 : 0x0000abab A11 : 0x00060023 A12 : 0x00060021 A13 : 0x3ffbc0d0
A14 : 0x00000003 A15 : 0x00060b23 SAR : 0x00000013 EXCCAUSE: 0x00000006
EXCVADDR: 0x00000000 LBEG : 0x00000000 LEND : 0x00000000 LCOUNT : 0x00000000
ELF file SHA256: 0000000000000000
Backtrace: 0x40086729:0x3ffbc020 0x40086bd3:0x3ffbc050 0x40088524:0x3ffbc070 0x400884da:0x3ffbc090 0x400893fb:0x00000000
Rebooting...
But I am getting this error when the interrupt is triggered. Please help me to resolve this

Answer 1

It's difficult to be sure as you didn't share any code, but... you should not update Preferences from an ISR. In fact unless you really really know what you're doing, you should do as little as possible inside an ISR.
Interrupts happen unpredictably... they literally interrupt whatever code is currently executing on the CPU. That means that any data structures the code is currently changing can be in an inconsistent state. Calling a function from the interrupt handler that uses those data structures will lead to data corruption and likely a crash.
Unless you wrote the code you're calling, you don't know what it calls. So you may say "it's okay, I'm not using Preferences outside the ISR" but you don't know what other functions Preferences calls.
You may get lucky and it may work at times... and it may also just crash randomly.
Again, unless you really really know what you're doing, there are very few functions that are safe to call inside an ISR. These are generally FreeRTOS functions that are explicitly designated as safe.
Interrupt handlers also block the CPU from doing other things it needs to do, so (unless you really really know what you're doing) you should minimize the amount of time you spend in the handler.
For most people who don't have experience writing interrupt handlers (especially people coding with the Arduino core), the best thing to do is the minimal work possible and set a flag that loop() inspects, and do the work in loop().
It's important that the flag be declared with the volatile keyword so that the compiler knows that its value can be changed unexpectedly.
It's also important that the interrupt handler be declared with IRAM_ATTR, to tell the system to keep its code loaded in instruction RAM so that it will be available when needed. Otherwise your program will crash if the code for the interrupt handler hasn't already been fetched from flash memory.
For instance:
volatile boolean interrupt_happened = false;
IRAM_ATTR void interrupt_handler() {
interrupt_happened = true;
}
void loop() {
if(interrupt_happened) {
do_some_work();
interrupt_happened = false;
}
}