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prevent self-deadlock with PICOLIBC due to calloc/realloc internally calling malloc/free #2069

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merged 2 commits into from
Nov 21, 2024
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prevent self-deadlock with PICOLIBC due to calloc/realloc internally calling malloc/free #2069

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prevent self-deadlock with PICOLIBC due to calloc/realloc internally …
kilograham Nov 20, 2024
b9b095e
comment tweaks
kilograham Nov 20, 2024
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65 changes: 41 additions & 24 deletions src/rp2_common/pico_malloc/malloc.c
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Original file line number Diff line number Diff line change
Expand Up @@ -24,6 +24,39 @@ extern void REAL_FUNC(free)(void *mem);

extern char __StackLimit; /* Set by linker. */

#if !PICO_USE_MALLOC_MUTEX
#define MALLOC_ENTER(outer) ((void)0);
#define MALLOC_EXIT(outer) ((void)0);
#elif !__PICOLIBC__
#define MALLOC_ENTER(outer) mutex_enter_blocking(&malloc_mutex);
#define MALLOC_EXIT(outer) mutex_exit(&malloc_mutex);
#else
static uint8_t mutex_exception_level_plus_one[NUM_CORES];
// PICOLIBC implementations of calloc and realloc may call malloc and free,
// so we need to cope with re-entrant calls. We don't want to use a recursive
// mutex as that won't catch usage within an ISR; instead we record the exception
// nesting as of acquiring the mutex
#define MALLOC_ENTER(outer) \
uint exception = __get_current_exception(); \
uint core_num = get_core_num(); \
/* we skip the locking on outer == false if we are in the same irq nesting */ \
/* note: the `+ 1` is to distinguish no malloc nesting vs no-exception/irq level */ \
bool do_lock = outer || exception + 1 != mutex_exception_level_plus_one[core_num]; \
if (do_lock) { \
mutex_enter_blocking(&malloc_mutex); \
if (outer) mutex_exception_level_plus_one[core_num] = (uint8_t)(exception + 1); \
}

#define MALLOC_EXIT(outer) \
if (outer) { \
mutex_exception_level_plus_one[core_num] = 0; \
} \
if (do_lock) { \
mutex_exit(&malloc_mutex); \
}

#endif

static inline void check_alloc(__unused void *mem, __unused uint size) {
#if PICO_MALLOC_PANIC
if (!mem || (((char *)mem) + size) > &__StackLimit) {
Expand All @@ -33,13 +66,9 @@ static inline void check_alloc(__unused void *mem, __unused uint size) {
}

void *WRAPPER_FUNC(malloc)(size_t size) {
#if PICO_USE_MALLOC_MUTEX
mutex_enter_blocking(&malloc_mutex);
#endif
MALLOC_ENTER(false)
void *rc = REAL_FUNC(malloc)(size);
#if PICO_USE_MALLOC_MUTEX
mutex_exit(&malloc_mutex);
#endif
MALLOC_EXIT(false)
#if PICO_DEBUG_MALLOC
if (!rc) {
printf("malloc %d failed to allocate memory\n", (uint) size);
Expand All @@ -52,13 +81,9 @@ void *WRAPPER_FUNC(malloc)(size_t size) {
}

void *WRAPPER_FUNC(calloc)(size_t count, size_t size) {
#if PICO_USE_MALLOC_MUTEX
mutex_enter_blocking(&malloc_mutex);
#endif
MALLOC_ENTER(true)
void *rc = REAL_FUNC(calloc)(count, size);
#if PICO_USE_MALLOC_MUTEX
mutex_exit(&malloc_mutex);
#endif
MALLOC_EXIT(true)
#if PICO_DEBUG_MALLOC
if (!rc) {
printf("calloc %d failed to allocate memory\n", (uint) (count * size));
Expand All @@ -71,13 +96,9 @@ void *WRAPPER_FUNC(calloc)(size_t count, size_t size) {
}

void *WRAPPER_FUNC(realloc)(void *mem, size_t size) {
#if PICO_USE_MALLOC_MUTEX
mutex_enter_blocking(&malloc_mutex);
#endif
MALLOC_ENTER(true)
void *rc = REAL_FUNC(realloc)(mem, size);
#if PICO_USE_MALLOC_MUTEX
mutex_exit(&malloc_mutex);
#endif
MALLOC_EXIT(true)
#if PICO_DEBUG_MALLOC
if (!rc) {
printf("realloc %d failed to allocate memory\n", (uint) size);
Expand All @@ -90,11 +111,7 @@ void *WRAPPER_FUNC(realloc)(void *mem, size_t size) {
}

void WRAPPER_FUNC(free)(void *mem) {
#if PICO_USE_MALLOC_MUTEX
mutex_enter_blocking(&malloc_mutex);
#endif
MALLOC_ENTER(false)
REAL_FUNC(free)(mem);
#if PICO_USE_MALLOC_MUTEX
mutex_exit(&malloc_mutex);
#endif
MALLOC_EXIT(false)
}
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