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LibC: Implement stdio FILE locking

This commit is contained in:
Bananymous 2025-04-02 12:45:44 +03:00
parent 9066e62a97
commit b9cc6063ff
1 changed files with 43 additions and 10 deletions
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53
userspace/libraries/LibC/stdio.cpp
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@ -1,10 +1,12 @@
#include <BAN/Assert.h>
#include <BAN/Debug.h>
#include <BAN/Atomic.h>
#include <BAN/Math.h>
#include <BAN/PlacementNew.h>
#include <bits/printf.h>
#include <errno.h>
#include <fcntl.h>
#include <pthread.h>
#include <scanf_impl.h>
#include <stdarg.h>
#include <stdio.h>
@ -31,7 +33,14 @@ struct FILE
unsigned char unget_buffer[12];
uint32_t unget_buf_idx;
// TODO: use recursive pthread_mutex when implemented?
// 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>);
struct ScopeLock
{
@ -88,8 +97,14 @@ static int drop_read_buffer(FILE* file)
void _init_stdio()
{
for (size_t i = 0; i < FOPEN_MAX; i++)
{
init_closed_file(&s_files[i]);
new (&s_files[i].locker()) BAN::Atomic<pthread_t>();
s_files[i].locker() = -1;
s_files[i].lock_depth = 0;
}
s_files[STDIN_FILENO].fd = STDIN_FILENO;
s_files[STDIN_FILENO].mode = O_RDONLY;
s_files[STDIN_FILENO].buffer_type = _IOLBF;
@ -170,7 +185,6 @@ FILE* fdopen(int fd, const char* mode_str)
return nullptr;
}
// FIXME: when threads are implemented
for (int i = 0; i < FOPEN_MAX; i++)
{
ScopeLock _(&s_files[i]);
@ -292,9 +306,20 @@ int fileno(FILE* fp)
return fp->fd;
}
void flockfile(FILE*)
void flockfile(FILE* fp)
{
// FIXME: when threads are implemented
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)
@ -310,7 +335,6 @@ FILE* fopen(const char* pathname, const char* mode_str)
if (fd == -1)
return nullptr;
// FIXME: when threads are implemented
for (int i = 0; i < FOPEN_MAX; i++)
{
ScopeLock _(&s_files[i]);
@ -458,15 +482,25 @@ off_t ftello(FILE* file)
return ret;
}
int ftrylockfile(FILE*)
int ftrylockfile(FILE* fp)
{
// FIXME: when threads are implemented
const pthread_t tid = pthread_self();
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*)
void funlockfile(FILE* fp)
{
// FIXME: when threads are implemented
ASSERT(fp->locker() == pthread_self());
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)
@ -706,7 +740,6 @@ FILE* popen(const char* command, const char* mode_str)
close(read ? fds[1] : fds[0]);
// FIXME: when threads are implemented
for (int i = 0; i < FOPEN_MAX; i++)
{
ScopeLock _(&s_files[i]);