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LibC: Use pthread_mutex on FILE instead of atomics

This commit is contained in:
Bananymous 2025-08-26 15:25:36 +03:00
parent abbe7b79d6
commit c6946d0145
1 changed files with 13 additions and 37 deletions
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50
userspace/libraries/LibC/stdio.cpp
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@ -34,11 +34,7 @@ struct FILE
unsigned char unget_buffer[12]; unsigned char unget_buffer[12];
uint32_t unget_buf_idx; uint32_t unget_buf_idx;
// TODO: use recursive pthread_mutex when implemented? pthread_mutex_t mutex;
// this storage hack is to keep FILE pod (init order)
BAN::Atomic<pthread_t>& locker() { return *reinterpret_cast<BAN::Atomic<pthread_t>*>(locker_storage); }
unsigned char locker_storage[sizeof(pthread_t)];
uint32_t lock_depth;
}; };
static_assert(BAN::is_pod_v<FILE>); static_assert(BAN::is_pod_v<FILE>);
@ -98,9 +94,11 @@ static void _init_stdio()
{ {
init_closed_file(&s_files[i]); init_closed_file(&s_files[i]);
new (&s_files[i].locker()) BAN::Atomic<pthread_t>(); pthread_mutexattr_t attr;
s_files[i].locker() = -1; pthread_mutexattr_init(&attr);
s_files[i].lock_depth = 0; pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE);
pthread_mutex_init(&s_files[i].mutex, &attr);
pthread_mutexattr_destroy(&attr);
} }
s_files[STDIN_FILENO].fd = STDIN_FILENO; s_files[STDIN_FILENO].fd = STDIN_FILENO;
@ -313,22 +311,6 @@ int fileno(FILE* fp)
return fp->fd; return fp->fd;
} }
void flockfile(FILE* fp)
{
const pthread_t tid = pthread_self();
pthread_t expected = -1;
while (!fp->locker().compare_exchange(expected, tid, BAN::MemoryOrder::memory_order_acq_rel))
{
if (expected == tid)
break;
sched_yield();
expected = -1;
}
fp->lock_depth++;
}
FILE* fopen(const char* pathname, const char* mode_str) FILE* fopen(const char* pathname, const char* mode_str)
{ {
mode_t mode = parse_mode_string(mode_str); mode_t mode = parse_mode_string(mode_str);
@ -485,25 +467,19 @@ off_t ftello(FILE* file)
return offset - file->unget_buf_idx; return offset - file->unget_buf_idx;
} }
void flockfile(FILE* fp)
{
pthread_mutex_lock(&fp->mutex);
}
int ftrylockfile(FILE* fp) int ftrylockfile(FILE* fp)
{ {
const pthread_t tid = pthread_self(); return pthread_mutex_trylock(&fp->mutex);
pthread_t expected = -1;
if (!fp->locker().compare_exchange(expected, tid, BAN::MemoryOrder::memory_order_acq_rel))
if (expected != tid)
return 1;
fp->lock_depth++;
return 0;
} }
void funlockfile(FILE* fp) void funlockfile(FILE* fp)
{ {
ASSERT(fp->locker() == pthread_self()); pthread_mutex_unlock(&fp->mutex);
ASSERT(fp->lock_depth > 0);
if (--fp->lock_depth == 0)
fp->locker().store(-1, BAN::MemoryOrder::memory_order_release);
} }
size_t fwrite(const void* buffer, size_t size, size_t nitems, FILE* file) size_t fwrite(const void* buffer, size_t size, size_t nitems, FILE* file)