On Wednesday 14 September 2016 10:44 AM, Dilger, Andreas wrote:
On Sep 12, 2016, at 04:27, Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
On Fri, Sep 09, 2016 at 08:50:35PM +0530, Nayeemahmed Badebade wrote:
Added __acquires / __releases sparse locking annotations
to lock_res_and_lock and unlock_res_and_lock functions in
l_lock.c, to fix below sparse warnings:
l_lock.c:47:22: warning: context imbalance in 'lock_res_and_lock' - wrong count at exit
l_lock.c:62:6: warning: context imbalance in 'unlock_res_and_lock' - unexpected unlock
Signed-off-by: Nayeemahmed Badebade <itachi.opsrc@xxxxxxxxx>
---
drivers/staging/lustre/lustre/ldlm/l_lock.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/drivers/staging/lustre/lustre/ldlm/l_lock.c b/drivers/staging/lustre/lustre/ldlm/l_lock.c
index ea8840c..c4b9612 100644
--- a/drivers/staging/lustre/lustre/ldlm/l_lock.c
+++ b/drivers/staging/lustre/lustre/ldlm/l_lock.c
@@ -45,6 +45,8 @@
* being an atomic operation.
*/
struct ldlm_resource *lock_res_and_lock(struct ldlm_lock *lock)
+ __acquires(&lock->l_lock)
+ __acquires(lock->l_resource)
Hm, these are tricky, I don't want to take this type of change without
an ack from the lustre developers...
The "__acquires(&lock->l_lock)" line here looks correct, along with the
corresponding "__releases(&lock->l_lock)" at unlock_res_and_lock().
The problem, however, is that "l_resource" is not a lock, but rather a
struct. The call to "lock_res(lock->l_resource)" is actually locking
"lr_lock" internally.
It would be better to add "__acquires(&res->lr_lock)" at lock_res() and
"__releases(&res->lr_lock)" at unlock_res(). That will also forestall
any other warnings about an imbalance with lock_res()/unlock_res() or
their callsites.
Cheers, Andreas
Hi Andreas,
Thank you for your review comments. I did the change according to your
comments and the diff is attached to mail. But this change doesn't seem
to fix the sparse warning.
With this change when i compile the code "make C=2
./drivers/staging/lustre/lustre/", sparse warning still comes:
{{{
CHECK drivers/staging/lustre/lustre/ptlrpc/../../lustre/ldlm/l_lock.c
drivers/staging/lustre/lustre/ptlrpc/../../lustre/ldlm/l_lock.c:47:22:
warning: context imbalance in 'lock_res_and_lock' - wrong count at exit
drivers/staging/lustre/lustre/ptlrpc/../../lustre/ldlm/l_lock.c:62:6:
warning: context imbalance in 'unlock_res_and_lock' - unexpected unlock
CC [M] drivers/staging/lustre/lustre/ptlrpc/../../lustre/ldlm/l_lock.o
}}}
Would it be a good idea to add "__acquires(&lock->l_resource->lr_lock)"
& "__acquires(&lock->l_lock)" at lock_res_and_lock() and
"__releases(&lock->l_resource->lr_lock)" & "__releases(&lock->l_lock)"
at unlock_res_and_lock() ?
Because with that change the sparse warning is fixed.
{{{
CHECK drivers/staging/lustre/lustre/ptlrpc/../../lustre/ldlm/l_lock.c
CC [M] drivers/staging/lustre/lustre/ptlrpc/../../lustre/ldlm/l_lock.o
}}}
Could you please confirm this.
Regards,
Nayeem
diff --git a/drivers/staging/lustre/lustre/include/lustre_dlm.h b/drivers/staging/lustre/lustre/include/lustre_dlm.h
index 1ec4231..2ae463a 100644
--- a/drivers/staging/lustre/lustre/include/lustre_dlm.h
+++ b/drivers/staging/lustre/lustre/include/lustre_dlm.h
@@ -1293,6 +1293,7 @@ enum lock_res_type {
/** Lock resource. */
static inline void lock_res(struct ldlm_resource *res)
+ __acquires(&res->lr_lock)
{
spin_lock(&res->lr_lock);
}
@@ -1306,6 +1307,7 @@ static inline void lock_res_nested(struct ldlm_resource *res,
/** Unlock resource. */
static inline void unlock_res(struct ldlm_resource *res)
+ __releases(&res->lr_lock)
{
spin_unlock(&res->lr_lock);
}
diff --git a/drivers/staging/lustre/lustre/ldlm/l_lock.c b/drivers/staging/lustre/lustre/ldlm/l_lock.c
index ea8840c..a887d9f 100644
--- a/drivers/staging/lustre/lustre/ldlm/l_lock.c
+++ b/drivers/staging/lustre/lustre/ldlm/l_lock.c
@@ -45,6 +45,7 @@
* being an atomic operation.
*/
struct ldlm_resource *lock_res_and_lock(struct ldlm_lock *lock)
+ __acquires(&lock->l_lock)
{
spin_lock(&lock->l_lock);
@@ -59,6 +60,7 @@ EXPORT_SYMBOL(lock_res_and_lock);
* Unlock a lock and its resource previously locked with lock_res_and_lock
*/
void unlock_res_and_lock(struct ldlm_lock *lock)
+ __releases(&lock->l_lock)
{
/* on server-side resource of lock doesn't change */
ldlm_clear_res_locked(lock);
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