When compiling the bcachefs-tools, the following compilation warning
is reported:
libbcachefs/six.c: In function ‘__do_six_trylock’:
libbcachefs/six.c:90:12: warning: ‘old’ may be used uninitialized in this
function [-Wmaybe-uninitialized]
90 | if (!(old & SIX_LOCK_HELD_intent)) {
| ~~~~~^~~~~~~~~~~~~~~~~~~~~~~
This is also a false altert. Only when @type=SIX_LOCK_write and @try=false
are passed in __do_six_trylock, the second condition branch would enter
which does not initialize the @old variable. But six_set_owner will not
use @old if @type is not SIX_LOCK_intent. There should be nothing wrong
in logical too.
Although the report itself is a false alert, we can elimate the unitialize
compilation warning by assigning @old in front.
Fixes: 84a37cbf62e0 ("six locks: Wakeup now takes lock on behalf of waiter")
Signed-off-by: Hongbo Li <[email protected]>
---
fs/bcachefs/six.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)
diff --git a/fs/bcachefs/six.c b/fs/bcachefs/six.c
index 3a494c5d1247..9f782e4e3ca9 100644
--- a/fs/bcachefs/six.c
+++ b/fs/bcachefs/six.c
@@ -118,11 +118,11 @@ static int __do_six_trylock(struct six_lock *lock, enum
six_lock_type type,
struct task_struct *task, bool try)
{
int ret;
- u32 old;
+ u32 old = atomic_read(&lock->state);
EBUG_ON(type == SIX_LOCK_write && lock->owner != task);
EBUG_ON(type == SIX_LOCK_write &&
- (try != !(atomic_read(&lock->state) & SIX_LOCK_HELD_write)));
+ (try != !(old & SIX_LOCK_HELD_write)));
/*
* Percpu reader mode:
@@ -157,7 +157,6 @@ static int __do_six_trylock(struct six_lock *lock, enum
six_lock_type type,
smp_mb();
- old = atomic_read(&lock->state);
ret = !(old & l[type].lock_fail);
this_cpu_sub(*lock->readers, !ret);
@@ -182,7 +181,6 @@ static int __do_six_trylock(struct six_lock *lock, enum
six_lock_type type,
ret = -1 - SIX_LOCK_read;
}
} else {
- old = atomic_read(&lock->state);
do {
ret = !(old & l[type].lock_fail);
if (!ret || (type == SIX_LOCK_write && !try)) {
--
2.34.1
