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SubjectRe: [peterz-queue:locking/core 41/43] kernel/locking/rwsem.c:1023:19: error: variable has incomplete type 'enum owner_state'
On Sat, Oct 16, 2021 at 02:41:17AM +0800, Xu, Yanfei wrote:
>
>
> On 10/15/21 9:51 PM, kernel test robot wrote:
> > [Please note: This e-mail is from an EXTERNAL e-mail address]
> >
> > tree: https://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git locking/core
> > head: 44e63f63c47dfb202eb25cdd97d04ec7e47f51d8
> > commit: b08614038dba3f6982e1e7701f23784bb0aedba6 [41/43] locking/rwsem: disable preemption for spinning region
> > config: hexagon-randconfig-r041-20211014 (attached as .config)
> > compiler: clang version 14.0.0 (https://github.com/llvm/llvm-project acb3b187c4c88650a6a717a1bcb234d27d0d7f54)
> > reproduce (this is a W=1 build):
> > wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
> > chmod +x ~/bin/make.cross
> > # https://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git/commit/?id=b08614038dba3f6982e1e7701f23784bb0aedba6
> > git remote add peterz-queue https://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git
> > git fetch --no-tags peterz-queue locking/core
> > git checkout b08614038dba3f6982e1e7701f23784bb0aedba6
> > # save the attached .config to linux build tree
> > mkdir build_dir
> > COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=hexagon SHELL=/bin/bash kernel/locking/
> >
> > If you fix the issue, kindly add following tag as appropriate
> > Reported-by: kernel test robot <lkp@intel.com>
> >
> > All errors (new ones prefixed by >>):
> >
> > > > kernel/locking/rwsem.c:1023:19: error: variable has incomplete type 'enum owner_state'
> > enum owner_state owner_state;
> > ^
> > kernel/locking/rwsem.c:1023:7: note: forward declaration of 'enum owner_state'
> > enum owner_state owner_state;
> > ^
> > 1 error generated.
> >
>
>
> Hi Peter,
>
> I send a patch named ("locking/rwsem: Introduce __rwsem_spin_on_owner()")
> for fixing this.

How about we do something like this instead? That makes the whole
CONFIG_RWSEM_SPIN_ON_OWNER=n side more consistent.


---

--- a/kernel/locking/rwsem.c
+++ b/kernel/locking/rwsem.c
@@ -577,6 +577,24 @@ static inline bool rwsem_try_write_lock(
return true;
}

+/*
+ * The rwsem_spin_on_owner() function returns the following 4 values
+ * depending on the lock owner state.
+ * OWNER_NULL : owner is currently NULL
+ * OWNER_WRITER: when owner changes and is a writer
+ * OWNER_READER: when owner changes and the new owner may be a reader.
+ * OWNER_NONSPINNABLE:
+ * when optimistic spinning has to stop because either the
+ * owner stops running, is unknown, or its timeslice has
+ * been used up.
+ */
+enum owner_state {
+ OWNER_NULL = 1 << 0,
+ OWNER_WRITER = 1 << 1,
+ OWNER_READER = 1 << 2,
+ OWNER_NONSPINNABLE = 1 << 3,
+};
+
#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
/*
* Try to acquire write lock before the writer has been put on wait queue.
@@ -632,23 +650,6 @@ static inline bool rwsem_can_spin_on_own
return ret;
}

-/*
- * The rwsem_spin_on_owner() function returns the following 4 values
- * depending on the lock owner state.
- * OWNER_NULL : owner is currently NULL
- * OWNER_WRITER: when owner changes and is a writer
- * OWNER_READER: when owner changes and the new owner may be a reader.
- * OWNER_NONSPINNABLE:
- * when optimistic spinning has to stop because either the
- * owner stops running, is unknown, or its timeslice has
- * been used up.
- */
-enum owner_state {
- OWNER_NULL = 1 << 0,
- OWNER_WRITER = 1 << 1,
- OWNER_READER = 1 << 2,
- OWNER_NONSPINNABLE = 1 << 3,
-};
#define OWNER_SPINNABLE (OWNER_NULL | OWNER_WRITER | OWNER_READER)

static inline enum owner_state
@@ -878,12 +879,11 @@ static inline bool rwsem_optimistic_spin

static inline void clear_nonspinnable(struct rw_semaphore *sem) { }

-static inline int
+static inline enum owner_state
rwsem_spin_on_owner(struct rw_semaphore *sem)
{
- return 0;
+ return OWNER_NONSPINNABLE;
}
-#define OWNER_NULL 1
#endif

/*
@@ -1095,9 +1095,16 @@ rwsem_down_write_slowpath(struct rw_sema
* In this case, we attempt to acquire the lock again
* without sleeping.
*/
- if (wstate == WRITER_HANDOFF &&
- rwsem_spin_on_owner(sem) == OWNER_NULL)
- goto trylock_again;
+ if (wstate == WRITER_HANDOFF) {
+ enum owner_state owner_state;
+
+ preempt_disable();
+ owner_state = rwsem_spin_on_owner(sem);
+ preempt_enable();
+
+ if (owner_state == OWNER_NULL)
+ goto trylock_again;
+ }

/* Block until there are no active lockers. */
for (;;) {
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