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QLockFile: Use fcntl for file locking on Android

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This commit updates the setNativeLocks function to use fcntl for file
locking on Android systems. Previously, the function attempted to use
flock, which would return false immediately upon failure in some cases.
By switching to fcntl, the function aims to provide more reliable lock
acquisition on Android.
This change is specific to Android systems and does not impact other
platforms where flock is used.

Fixes: QTBUG-116511
Pick-to: 6.8 6.7 6.5 6.2 5.15
Change-Id: Ifb93cb6a8aec801539ba378c23d9b1ada3f069bb
Reviewed-by: Ville Voutilainen <ville.voutilainen@qt.io>
This commit is contained in:
Ahmed El Khazari 2024-06-11 19:39:05 +03:00
parent 877b29a78e
commit 3b8e8bd081
1 changed files with 16 additions and 2 deletions
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18
src/corelib/io/qlockfile_unix.cpp
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@ -101,12 +101,26 @@ static qint64 qt_write_loop(int fd, const char *data, qint64 len)
* actually the same. Therefore, it's a very bad idea to mix them in the same
* process.
*
* We therefore use only flock(2).
* We therefore use only flock(2), except on Android.
*
* Android Compatibility:
* Some versions of Android have known issues where flock does not function correctly. 
* As a result, on Android, we use POSIX fcntl(F_SETLK) to handle file locking.
* fcntl is better integrated with Android’s underlying system, avoiding
* the limitations of flock.
*/
static bool setNativeLocks(int fd)
{
#if defined(LOCK_EX) && defined(LOCK_NB)
#if defined(Q_OS_ANDROID)
struct flock fl;
fl.l_type = F_WRLCK;
fl.l_whence = SEEK_SET;
fl.l_start = 0;
fl.l_len = 0;
if (fcntl(fd, F_SETLK, &fl) == -1)
return false;
#elif defined(LOCK_EX) && defined(LOCK_NB)
if (flock(fd, LOCK_EX | LOCK_NB) == -1) // other threads, and other processes on a local fs
return false;
#else