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Fix possible IRQ worker starvation in release gcc 10 builds in stdio_usb #364

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Merged
kilograham merged 1 commit into from
May 4, 2021
Merged

Fix possible IRQ worker starvation in release gcc 10 builds in stdio_usb #364

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1 change: 1 addition & 0 deletions src/rp2_common/pico_stdio/CMakeLists.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -11,6 +11,7 @@ if (NOT TARGET pico_stdio)
pico_wrap_function(pico_stdio vprintf)
pico_wrap_function(pico_stdio puts)
pico_wrap_function(pico_stdio putchar)
pico_wrap_function(pico_stdio getchar)

if (TARGET pico_printf)
target_link_libraries(pico_stdio INTERFACE pico_printf)
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10 changes: 6 additions & 4 deletions src/rp2_common/pico_stdio/stdio.c
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Expand Up @@ -123,7 +123,9 @@ static int stdio_get_until(char *buf, int len, absolute_time_t until) {
}
}
}
// todo maybe a little sleep here?
// we sleep here in case the in_chars methods acquire mutexes or disable IRQs and
// potentially starve out what they are waiting on (have seen this with USB)
busy_wait_us(1);
} while (!time_reached(until));
return PICO_ERROR_TIMEOUT;
}
Expand Down Expand Up @@ -257,9 +259,9 @@ void stdio_init_all() {

int WRAPPER_FUNC(getchar)(void) {
char buf[1];
if (0 == stdio_get_until(buf, sizeof(buf), at_the_end_of_time)) {
return PICO_ERROR_TIMEOUT;
}
int len = stdio_get_until(buf, 1, at_the_end_of_time);
if (len < 0) return len;
assert(len == 1);
return (uint8_t)buf[0];
}

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