Armando 6a1bfa29b0 SPI_BUS_LOCK: fix a concurrency issue ...

define: lock_bits = (lock->status & LOCK_MASK) >> LOCK_SHIFT;  This `lock_bits` is the Bit 29-20 of the lock->status

1. spi_hdl_1:
   acquire_end_core():
   uint32_t status = lock_status_clear(lock, dev_handle->mask & LOCK_MASK);
   Becuase this is the first `spi_hdl_1`, so after this , lock_bits == 0`b0. status == 0

2. spi_hdl_2:
   acquire_core:
   uint32_t status = lock_status_fetch_set(lock, dev_handle->mask & LOCK_MASK);
   Then here status is 0`b0, but lock_bits == 0`b10. Because this is the `spi_hdl_2`

3. spi_hdl_2:
   `acquire_core` return true, because status == 0. `spi_bus_lock_acquire_start(spi_hdl_2)` then won't block.

4. spi_hdl_2:
   spi_device_polling_end(spi_hdl_2).

5. spi_hdl_1:
   acquire_end_core:
   status is 0, so it cleas the lock->acquiring_dev

6. spi_hdl_2:
   spi_device_polling_end:
   assert(handle == get_acquiring_dev(host)); Fail

Closes https://github.com/espressif/esp-idf/issues/8179

2022-09-14 12:13:24 +08:00

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