make -j flash broken on esp* (will always flash the previous binary)

[benpicco]

Description

I'm a habitual user of make -j. It looks like the build system has developed a very reliable race condition where a make -j flash will always flash the previous binary on esp*.

Steps to reproduce the issue

• In examples/hello-world run make BOARD=esp32-wroom-32 -j flash term.
• change the text in main.c, better yet print it in a while(1) loop
• run make BOARD=esp32-wroom-32 -j flash term again

Expected results

• the new text is printed

Actual results

• the old text is printed.
• run make BOARD=esp32-wroom-32 -j flash term again
• the new text is printed.

Workaround

• run make BOARD=esp32-wroom-32 -j && make BOARD=esp32-wroom-32 flash term

Versions

xtensa-esp32-elf-gcc (crosstool-NG crosstool-ng-1.22.0-80-g6c4433a5) 5.2.0
GNU Make 4.2.1

[gschorcht]

Hm, strange and not really clear why. I used tests/shell for my tests. main.c is definitly recompiled and the change is in ELF file tests_shell.elf. I have checked this by renaming a function in main.c.

[gschorcht]

It seems that it starts preflash target before the tests_shell.elf has been updated. At least I can observe with QUIET=0 that the following preparation of the flash file is executed before the compilation of the ELF file tests_shell.elf has been finished:

RIOT/cpu/esp_common/Makefile.include

Lines 96 to 106 in 2d1d13d

	# configure preflasher to convert .elf to .bin before flashing
	PREFLASHER = $(ESPTOOL)
	PREFFLAGS = --chip $(FLASH_CHIP) elf2image
	PREFFLAGS += --flash_mode $(FLASH_MODE) --flash_size $(FLASH_SIZE)MB
	PREFFLAGS += --flash_freq $(FLASH_FREQ) $(FLASH_OPTS)
	PREFFLAGS += -o $(FLASHFILE).bin $(FLASHFILE);
	PREFFLAGS += printf "\n" > $(BINDIR)/partitions.csv;
	PREFFLAGS += printf "nvs, data, nvs, 0x9000, 0x6000\n" >> $(BINDIR)/partitions.csv;
	PREFFLAGS += printf "phy_init, data, phy, 0xf000, 0x1000\n" >> $(BINDIR)/partitions.csv;
	PREFFLAGS += printf "factory, app, factory, 0x10000, " >> $(BINDIR)/partitions.csv;
	PREFFLAGS += ls -l $(FLASHFILE).bin | awk '{ print $$5 }' >> $(BINDIR)/partitions.csv;

This part is executed by the preflash target and flash depends on preflash

RIOT/cpu/esp_common/Makefile.include

Line 110 in 2d1d13d

FLASHDEPS += preflash

So it seems to be a missing dependency of the preflash target on the ELF file. Maybe I misinterpreted the preflash target when I wrote the makefiles. I thought it is a target that is executed before an ELF file is flashed. But obviously it only depends on the BUILD_BEFORE_FLASH variable which isn't set anywhere

RIOT/Makefile.include

Line 702 in 2d1d13d

preflash: $(BUILD_BEFORE_FLASH)

There are two options to solve the problem. Either we move the code for the preparation of the flash binary to the flash target or we just set the variable

BUILD_BEFORE_FLASH += $(FLASHFILE)

[gschorcht]

The fix in PR #14041 had to be reverted for the moment.

[jenswet]

I can reproduce the same problem on the current master.