ESP32 Wrover Module
arduino-esp32 v1.0.2

I discovered a problem that happens when an spi_slave interrupt occurs during SPIFFS access.
I have the spi_slave initialized to use DMA, and get the following error when this occurs:

Guru Meditation Error: Core 1 panic'ed (Cache disabled but cached memory region accessed)

From the following Exception Decoder listing it must be that the SPIFFS disables cache (which is expected and normal) and when the spi_slave interrupt happens the "freeze_cs" function generates an exception since it is in flash and not in RAM.

Looking at the "spi_slave.c" file, one can see that the "static void freeze_cs" function is indeed a function not in RAM. I believe this is a mistake, since there is a corresponding "static inline void restore_cs" function than will be placed in RAM since it's an inline function and the calling ISR function is in RAM.

Proposed solution is to change:
static void freeze_cs(spi_slave_t *host)
to:
static inline void freeze_cs(spi_slave_t *host)

Does this change make sense?

I'd like to make the change and test it, but I do not know how to recompile to generate an updated library file for esp32-arduino. Can anyone provide instructions on how to make this change to the library?

Thanks!

Decoding stack results
0x400e7f58: freeze_cs at /Users/ficeto/Desktop/ESP32/ESP32/esp-idf-public/components/driver/spi_slave.c line 89
0x400954bf: esp_rom_spiflash_read_status at /Users/ficeto/Desktop/ESP32/ESP32/esp-idf-public/components/spi_flash/spi_flash_rom_patch.c line 261
0x400954f6: esp_rom_spiflash_wait_idle at /Users/ficeto/Desktop/ESP32/ESP32/esp-idf-public/components/spi_flash/spi_flash_rom_patch.c line 35
0x40095595: esp_rom_spiflash_erase_sector_internal at /Users/ficeto/Desktop/ESP32/ESP32/esp-idf-public/components/spi_flash/spi_flash_rom_patch.c line 121
0x40095a2a: esp_rom_spiflash_erase_sector at /Users/ficeto/Desktop/ESP32/ESP32/esp-idf-public/components/spi_flash/spi_flash_rom_patch.c line 451
0x40082d59: spi_flash_erase_range at /Users/ficeto/Desktop/ESP32/ESP32/esp-idf-public/components/spi_flash/flash_ops.c line 237
0x400f6419: esp_partition_erase_range at /Users/ficeto/Desktop/ESP32/ESP32/esp-idf-public/components/spi_flash/partition.c line 294
0x400fd723: spiffs_api_erase at /Users/ficeto/Desktop/ESP32/ESP32/esp-idf-public/components/spiffs/spiffs_api.c line 58
0x400ff13e: spiffs_erase_block at /Users/ficeto/Desktop/ESP32/ESP32/esp-idf-public/components/spiffs/spiffs/src/spiffs_nucleus.c line 236
0x40101a91: spiffs_gc_erase_block at /Users/ficeto/Desktop/ESP32/ESP32/esp-idf-public/components/spiffs/spiffs/src/spiffs_gc.c line 15
0x40101bff: spiffs_gc_quick at /Users/ficeto/Desktop/ESP32/ESP32/esp-idf-public/components/spiffs/spiffs/src/spiffs_gc.c line 92
0x400ff3c9: spiffs_obj_lu_find_free at /Users/ficeto/Desktop/ESP32/ESP32/esp-idf-public/components/spiffs/spiffs/src/spiffs_nucleus.c line 457
0x400ff718: spiffs_page_move at /Users/ficeto/Desktop/ESP32/ESP32/esp-idf-public/components/spiffs/spiffs/src/spiffs_nucleus.c line 828
0x400ffcf6: spiffs_object_update_index_hdr at /Users/ficeto/Desktop/ESP32/ESP32/esp-idf-public/components/spiffs/spiffs/src/spiffs_nucleus.c line 1019
0x400fe778: SPIFFS_fupdate_meta at /Users/ficeto/Desktop/ESP32/ESP32/esp-idf-public/components/spiffs/spiffs/src/spiffs_hydrogen.c line 988
0x400fd229: vfs_spiffs_update_mtime at /Users/ficeto/Desktop/ESP32/ESP32/esp-idf-public/components/spiffs/esp_spiffs.c line 731
0x400fd299: vfs_spiffs_open at /Users/ficeto/Desktop/ESP32/ESP32/esp-idf-public/components/spiffs/esp_spiffs.c line 458
0x400f326a: esp_vfs_open at /Users/ficeto/Desktop/ESP32/ESP32/esp-idf-public/components/vfs/vfs.c line 388
0x400f4c2d: _fopen_r at ../../../.././newlib/libc/stdio/fopen.c line 141
0x400f4cb4: fopen at ../../../.././newlib/libc/stdio/fopen.c line 181
0x400d6986: VFSFileImpl::VFSFileImpl(VFSImpl*, char const*, char const*) at C:\Users\DMD\Documents\Arduino\hardware\expressif\esp32\libraries\FS\src\vfs_api.cpp line 236
0x400d6e4f: std::__shared_ptr ::__shared_ptr , VFSImpl*&, char const*, char const*&>(std::_Sp_make_shared_tag, std::allocator const&, VFSImpl*&, char const*&&, char const*&) at c:\users\dmd\appdata\local\arduino15\packages\esp32\tools\xtensa-esp32-elf-gcc\1.22.0-80-g6c4433a-5.2.0\xtensa-esp32-elf\include\c++\5.2.0\ext/new_allocator.h line 120
0x400d7165: VFSImpl::open(char const*, char const*) at c:\users\dmd\appdata\local\arduino15\packages\esp32\tools\xtensa-esp32-elf-gcc\1.22.0-80-g6c4433a-5.2.0\xtensa-esp32-elf\include\c++\5.2.0\bits/shared_ptr.h line 319
0x400d65c8: fs::FS::open(char const*, char const*) at C:\Users\DMD\Documents\Arduino\hardware\expressif\esp32\libraries\FS\src\FS.cpp line 191
0x400d35e6: loop() at C:\Users\DMD\Documents\Arduino\DMD_Sketches\DMD_WiFi/DMD_WiFi.ino line 506
0x400e5af1: loopTask(void*) at C:\Users\DMD\Documents\Arduino\hardware\expressif\esp32\cores\esp32\main.cpp line 19
0x4008b3ad: vPortTaskWrapper at /Users/ficeto/Desktop/ESP32/ESP32/esp-idf-public/components/freertos/port.c line 143