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Fix multicore_lockout features so that the victim core cannot become stuck in an infinite loop if the lockout attempt times out #2467

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Merged
merged 5 commits into from
May 20, 2025
Merged

Fix multicore_lockout features so that the victim core cannot become stuck in an infinite loop if the lockout attempt times out #2467

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e91da36
Fix issue 2454 flash safe execute lockout
jwhitham May 13, 2025
eadf08b
Update documentation for multicore_lockout_end functions
jwhitham May 14, 2025
5551101
Simplification, remove magic number (not required)
jwhitham May 15, 2025
d928e45
Review improvements
jwhitham May 16, 2025
38de127
Restore use of non-zero magic number
jwhitham May 17, 2025
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53 changes: 33 additions & 20 deletions src/rp2_common/pico_multicore/multicore.c
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Original file line number Diff line number Diff line change
Expand Up @@ -203,24 +203,26 @@ void multicore_launch_core1_raw(void (*entry)(void), uint32_t *sp, uint32_t vect
}

#define LOCKOUT_MAGIC_START 0x73a8831eu
#define LOCKOUT_MAGIC_END (~LOCKOUT_MAGIC_START)

static mutex_t lockout_mutex;
static bool lockout_in_progress;
static io_rw_32 lockout_request_id = LOCKOUT_MAGIC_START;

// note this method is in RAM because lockout is used when writing to flash
// it only makes inline calls
static void __isr __not_in_flash_func(multicore_lockout_handler)(void) {
multicore_fifo_clear_irq();
while (multicore_fifo_rvalid()) {
if (sio_hw->fifo_rd == LOCKOUT_MAGIC_START) {
uint32_t request_id = sio_hw->fifo_rd;
if (request_id == lockout_request_id) {
// valid lockout request received
uint32_t save = save_and_disable_interrupts();
multicore_fifo_push_blocking_inline(LOCKOUT_MAGIC_START);
while (multicore_fifo_pop_blocking_inline() != LOCKOUT_MAGIC_END) {
tight_loop_contents(); // not tight but endless potentially
multicore_fifo_push_blocking_inline(request_id);
// wait for the lockout to expire
while (request_id == lockout_request_id) {
// when lockout_request_id is updated, the other CPU core calls __sev
__wfe();
}
restore_interrupts_from_disabled(save);
multicore_fifo_push_blocking_inline(LOCKOUT_MAGIC_END);
}
}
}
Expand Down Expand Up @@ -257,7 +259,7 @@ void multicore_lockout_victim_deinit(void) {
}
}

static bool multicore_lockout_handshake(uint32_t magic, absolute_time_t until) {
static bool multicore_lockout_handshake(uint32_t request_id, absolute_time_t until) {
uint irq_num = SIO_FIFO_IRQ_NUM(get_core_num());
bool enabled = irq_is_enabled(irq_num);
if (enabled) irq_set_enabled(irq_num, false);
Expand All @@ -267,7 +269,7 @@ static bool multicore_lockout_handshake(uint32_t magic, absolute_time_t until) {
if (next_timeout_us < 0) {
break;
}
multicore_fifo_push_timeout_us(magic, (uint64_t)next_timeout_us);
multicore_fifo_push_timeout_us(request_id, (uint64_t)next_timeout_us);
next_timeout_us = absolute_time_diff_us(get_absolute_time(), until);
if (next_timeout_us < 0) {
break;
Expand All @@ -276,22 +278,36 @@ static bool multicore_lockout_handshake(uint32_t magic, absolute_time_t until) {
if (!multicore_fifo_pop_timeout_us((uint64_t)next_timeout_us, &word)) {
break;
}
if (word == magic) {
if (word == request_id) {
rc = true;
}
} while (!rc);
if (enabled) irq_set_enabled(irq_num, true);
return rc;
}

static uint32_t update_lockout_request_id() {
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can you add a (void) i'm pretty sure without this it makes at least one of the many GCC or Clang compiler versions unhappy

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Thanks, fixed.

// generate new number and then update shared variable
uint32_t new_request_id = lockout_request_id + 1;
lockout_request_id = new_request_id;
// notify other core
__sev();
return new_request_id;
}

static bool multicore_lockout_start_block_until(absolute_time_t until) {
check_lockout_mutex_init();
if (!mutex_enter_block_until(&lockout_mutex, until)) {
return false;
}
hard_assert(!lockout_in_progress);
bool rc = multicore_lockout_handshake(LOCKOUT_MAGIC_START, until);
lockout_in_progress = rc;
// generate a new request_id number
uint32_t request_id = update_lockout_request_id();
// attempt to lock out
bool rc = multicore_lockout_handshake(request_id, until);
if (!rc) {
// lockout failed - cancel it
update_lockout_request_id();
}
mutex_exit(&lockout_mutex);
return rc;
}
Expand All @@ -309,13 +325,10 @@ static bool multicore_lockout_end_block_until(absolute_time_t until) {
if (!mutex_enter_block_until(&lockout_mutex, until)) {
return false;
}
assert(lockout_in_progress);
bool rc = multicore_lockout_handshake(LOCKOUT_MAGIC_END, until);
if (rc) {
lockout_in_progress = false;
}
// lockout finished - cancel it
update_lockout_request_id();
mutex_exit(&lockout_mutex);
return rc;
return true;
}

bool multicore_lockout_end_timeout_us(uint64_t timeout_us) {
Expand Down Expand Up @@ -402,4 +415,4 @@ void multicore_doorbell_unclaim(uint doorbell_num, uint core_mask) {
}


#endif
#endif