| Subject: rwlocks: Fix section mismatch |
| From: John Kacur <jkacur@redhat.com> |
| Date: Mon, 19 Sep 2011 11:09:27 +0200 (CEST) |
| |
| This fixes the following build error for the preempt-rt kernel. |
| |
| make kernel/fork.o |
| CC kernel/fork.o |
| kernel/fork.c:90: error: section of ¡tasklist_lock¢ conflicts with previous declaration |
| make[2]: *** [kernel/fork.o] Error 1 |
| make[1]: *** [kernel/fork.o] Error 2 |
| |
| The rt kernel cache aligns the RWLOCK in DEFINE_RWLOCK by default. |
| The non-rt kernels explicitly cache align only the tasklist_lock in |
| kernel/fork.c |
| That can create a build conflict. This fixes the build problem by making the |
| non-rt kernels cache align RWLOCKs by default. The side effect is that |
| the other RWLOCKs are also cache aligned for non-rt. |
| |
| This is a short term solution for rt only. |
| The longer term solution would be to push the cache aligned DEFINE_RWLOCK |
| to mainline. If there are objections, then we could create a |
| DEFINE_RWLOCK_CACHE_ALIGNED or something of that nature. |
| |
| Comments? Objections? |
| |
| Signed-off-by: John Kacur <jkacur@redhat.com> |
| Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> |
| Link: http://lkml.kernel.org/r/alpine.LFD.2.00.1109191104010.23118@localhost6.localdomain6 |
| Signed-off-by: Thomas Gleixner <tglx@linutronix.de> |
| --- |
| include/linux/rwlock_types.h | 3 ++- |
| kernel/fork.c | 2 +- |
| 2 files changed, 3 insertions(+), 2 deletions(-) |
| |
| --- a/include/linux/rwlock_types.h |
| +++ b/include/linux/rwlock_types.h |
| @@ -47,6 +47,7 @@ typedef struct { |
| RW_DEP_MAP_INIT(lockname) } |
| #endif |
| |
| -#define DEFINE_RWLOCK(x) rwlock_t x = __RW_LOCK_UNLOCKED(x) |
| +#define DEFINE_RWLOCK(name) \ |
| + rwlock_t name __cacheline_aligned_in_smp = __RW_LOCK_UNLOCKED(name) |
| |
| #endif /* __LINUX_RWLOCK_TYPES_H */ |
| --- a/kernel/fork.c |
| +++ b/kernel/fork.c |
| @@ -93,7 +93,7 @@ int max_threads; /* tunable limit on nr |
| |
| DEFINE_PER_CPU(unsigned long, process_counts) = 0; |
| |
| -__cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */ |
| +DEFINE_RWLOCK(tasklist_lock); /* outer */ |
| |
| #ifdef CONFIG_PROVE_RCU |
| int lockdep_tasklist_lock_is_held(void) |