rp2/rp2_flash: Workaround multicore lockout not being reset.

With regression test.

See upstream bug https://github.com/raspberrypi/pico-sdk/issues/2201

Tested-by: Angus Gratton <angus@redyak.com.au>
Signed-off-by: Mike Bell <mdb036@gmail.com>

ports/rp2/rp2_flash.c

@@ -70,10 +70,20 @@ bi_decl(bi_block_device(
     BINARY_INFO_BLOCK_DEV_FLAG_WRITE |
     BINARY_INFO_BLOCK_DEV_FLAG_PT_UNKNOWN));
 
+// This is a workaround to pico-sdk #2201: https://github.com/raspberrypi/pico-sdk/issues/2201
+// which means the multicore_lockout_victim_is_initialized returns true even after core1 is reset.
+static bool use_multicore_lockout(void) {
+    return multicore_lockout_victim_is_initialized(1 - get_core_num())
+           #if MICROPY_PY_THREAD
+           && core1_entry != NULL
+           #endif
+    ;
+}
+
 // Flash erase and write must run with interrupts disabled and the other core suspended,
 // because the XIP bit gets disabled.
 static uint32_t begin_critical_flash_section(void) {
-    if (multicore_lockout_victim_is_initialized(1 - get_core_num())) {
+    if (use_multicore_lockout()) {
         multicore_lockout_start_blocking();
     }
     return save_and_disable_interrupts();
@@ -81,7 +91,7 @@ static uint32_t begin_critical_flash_section(void) {
 
 static void end_critical_flash_section(uint32_t state) {
     restore_interrupts(state);
-    if (multicore_lockout_victim_is_initialized(1 - get_core_num())) {
+    if (use_multicore_lockout()) {
         multicore_lockout_end_blocking();
     }
 }

tests/ports/rp2/rp2_thread_reset_part1.py

@@ -0,0 +1,18 @@
+# This is a regression test for https://github.com/micropython/micropython/issues/16619
+# it runs in two parts by necessity:
+#
+# - This "part1" creates a non-terminating thread.
+# - The test runner issues a soft reset, which will terminate that thread.
+# - "part2" is the actual test, which is whether flash access works correctly
+#   after the thread was terminated by soft reset.
+
+import _thread
+
+
+def infinite():
+    while True:
+        pass
+
+
+_thread.start_new_thread(infinite, ())
+print("Part 1 complete...")

tests/ports/rp2/rp2_thread_reset_part1.py.exp

@@ -0,0 +1 @@
+Part 1 complete...

tests/ports/rp2/rp2_thread_reset_part2.py

@@ -0,0 +1,12 @@
+# This is part2 of a two-part regression test, see part1
+# for details of what's expected.
+import os
+
+FILENAME = "/rp2_thread_reset_test.txt"
+
+print("Starting")
+with open(FILENAME, "w") as f:
+    f.write("test")
+print("Written")
+os.unlink(FILENAME)
+print("Removed")

tests/ports/rp2/rp2_thread_reset_part2.py.exp

@@ -0,0 +1,3 @@
+Starting
+Written
+Removed