luc14n0/glib
1
0
Fork 0
mirror of https://gitlab.gnome.org/GNOME/glib.git synced 2024-11-10 03:16:17 +01:00
Code Issues Packages Projects Releases Wiki Activity

Merge branch 'cond-wait-mips24' into 'main'

Browse Source 
gthread: Fix futex timespec type on 32-bit kernels with 64-bit userspace

Closes #2634

See merge request GNOME/glib!2622
This commit is contained in:
Philip Withnall 2022-05-05 16:49:04 +00:00
commit 5ea0ecf8c7
1 changed files with 32 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

33
glib/gthread-posix.c
View File

@ -1599,6 +1599,13 @@ g_cond_wait_until (GCond *cond,
{
struct timespec now;
struct timespec span;
#ifdef __NR_futex_time64
long span_arg[2];
G_STATIC_ASSERT (sizeof (span_arg[0]) == 4);
#else
struct timespec span_arg;
#endif
guint sampled;
int res;
gboolean success;
@ -1618,9 +1625,33 @@ g_cond_wait_until (GCond *cond,
if (span.tv_sec < 0)
return FALSE;
/* On x32 (ILP32 ABI on x86_64) and potentially sparc64, the raw futex()
* syscall takes a 32-bit timespan argument *regardless* of whether userspace
* is using 32-bit or 64-bit `struct timespec`. This means that we can’t
* unconditionally pass a `struct timespec` pointer into the syscall.
*
* Assume that any such platform is new enough to define the
* `__NR_futex_time64` workaround syscall (which accepts 64-bit timespecs,
* introduced in kernel 5.1), and use that as a proxy for whether to pass in
* `long[2]` or `struct timespec`.
*
* As per https://lwn.net/Articles/776427/, the `time64` syscalls only exist
* on 32-bit platforms, so in this case `sizeof(long)` should always be
* 32 bits.
*
* Don’t bother actually calling `__NR_futex_time64` as the `span` is relative
* and hence very unlikely to overflow, even if using 32-bit longs.
*/
#ifdef __NR_futex_time64
span_arg[0] = span.tv_sec;
span_arg[1] = span.tv_nsec;
#else
span_arg = span;
#endif
sampled = cond->i[0];
g_mutex_unlock (mutex);
res = syscall (__NR_futex, &cond->i[0], (gsize) FUTEX_WAIT_PRIVATE, (gsize) sampled, &span);
res = syscall (__NR_futex, &cond->i[0], (gsize) FUTEX_WAIT_PRIVATE, (gsize) sampled, &span_arg);
success = (res < 0 && errno == ETIMEDOUT) ? FALSE : TRUE;
g_mutex_lock (mutex);