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fs/vfs/fs_lock.c: fix flock behavior for more threads and fds

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We need to use gettid instead of getpid, otherwise flocks applied
from different threads are considered as single thread lock and are
ignored (or updated).

Also fix the behavior if process opens the file multiple times
Linux/BSD manual states multiple file descriptors opened by a single
process shall be treated independently. Therefore we also need to
compare struct file pointer to determine whether the lock applies
to the same descriptor or not.

Signed-off-by: Michal Lenc <michallenc@seznam.cz>
This commit is contained in:
Michal Lenc 2026-06-04 13:20:44 +02:00 • committed by Lup Yuen Lee
parent 1a3185beeb
commit 726dd10bcd
1 changed files with 12 additions and 10 deletions
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22
fs/vfs/fs_lock.c
View file

@ -260,18 +260,20 @@ static void file_lock_delete_bucket(FAR struct file_lock_bucket_s *bucket,
****************************************************************************/
static bool file_lock_is_conflict(FAR struct flock *request,
FAR struct flock *internal)
FAR struct file *request_filep,
FAR struct file_lock_s *internal)
{
/* If the request is not exactly to the left or right of the internal,
* then there is an overlap.
*/
if (request->l_start <= internal->l_end && request->l_end >=
internal->l_start)
if (request->l_start <= internal->fl_lock.l_end && request->l_end >=
internal->fl_lock.l_start)
{
if (request->l_type == F_WRLCK || internal->l_type == F_WRLCK)
if (request->l_type == F_WRLCK || internal->fl_lock.l_type == F_WRLCK)
{
return request->l_pid != internal->l_pid;
return request->l_pid != internal->fl_lock.l_pid ||
request_filep != internal->fl_file;
}
}
@ -371,8 +373,8 @@ static int file_lock_modify(FAR struct file *filep,
{
if (request->l_pid != file_lock->fl_lock.l_pid)
{
/* Only file locks with the same pid need to be processed, so the
* lookup is skipped.
/* Only file locks with the same thread id need to be
* processed, so the lookup is skipped.
*/
if (find)
@ -598,7 +600,7 @@ int file_getlk(FAR struct file *filep, FAR struct flock *flock)
list_for_every_entry(&bucket->list, file_lock, struct file_lock_s,
fl_node)
{
if (file_lock_is_conflict(flock, &file_lock->fl_lock))
if (file_lock_is_conflict(flock, filep, file_lock))
{
memcpy(flock, &file_lock->fl_lock, sizeof(*flock));
goto out;
@ -677,7 +679,7 @@ int file_setlk(FAR struct file *filep, FAR struct flock *flock,
goto out_free;
}
request.l_pid = getpid();
request.l_pid = gettid();
nxmutex_lock(&g_protect_lock);
@ -709,7 +711,7 @@ retry:
list_for_every_entry(&bucket->list, file_lock, struct file_lock_s,
fl_node)
{
if (file_lock_is_conflict(&request, &file_lock->fl_lock))
if (file_lock_is_conflict(&request, filep, file_lock))
{
if (nonblock)
{