Module: xenomai-jki
Branch: for-upstream
Commit: ea98452b8643e324bd4f56bf110ced16a39749d2
URL:    
http://git.xenomai.org/?p=xenomai-jki.git;a=commit;h=ea98452b8643e324bd4f56bf110ced16a39749d2

Author: Jan Kiszka <jan.kis...@siemens.com>
Date:   Fri Apr  2 10:21:29 2010 +0200

RTDM: Instrument rtdm_context_lock/unlock to detect misuses

rtdm_context_lock must only be called on context structures that are
already locked, and rtdm_context_unlock must be kept in balance with
rtdm_context_get/rtdm_context_lock. Try to check for mistakes by
requiring non-null clock_lock_count on entry of both services.

Also fix a typo and clarify the use cases and restrictions of
rtdm_context_lock.

CC: Philippe Gerum <r...@xenomai.org>
Signed-off-by: Jan Kiszka <jan.kis...@siemens.com>

---

 include/rtdm/rtdm_driver.h |    4 ++++
 ksrc/skins/rtdm/core.c     |   10 +++++++---
 2 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/include/rtdm/rtdm_driver.h b/include/rtdm/rtdm_driver.h
index 7d5983c..310df09 100644
--- a/include/rtdm/rtdm_driver.h
+++ b/include/rtdm/rtdm_driver.h
@@ -555,11 +555,15 @@ struct rtdm_dev_context *rtdm_context_get(int fd);
 #ifndef DOXYGEN_CPP /* Avoid static inline tags for RTDM in doxygen */
 static inline void rtdm_context_lock(struct rtdm_dev_context *context)
 {
+       XENO_ASSERT(RTDM, atomic_read(&context->close_lock_count) > 0,
+                   /* just warn if context was a dangling pointer */);
        atomic_inc(&context->close_lock_count);
 }
 
 static inline void rtdm_context_unlock(struct rtdm_dev_context *context)
 {
+       XENO_ASSERT(RTDM, atomic_read(&context->close_lock_count) > 0,
+                   /* just warn if context was a dangling pointer */);
        smp_mb__before_atomic_dec();
        atomic_dec(&context->close_lock_count);
 }
diff --git a/ksrc/skins/rtdm/core.c b/ksrc/skins/rtdm/core.c
index 8cccf52..ba4dc63 100644
--- a/ksrc/skins/rtdm/core.c
+++ b/ksrc/skins/rtdm/core.c
@@ -87,7 +87,7 @@ struct rtdm_dev_context *rtdm_context_get(int fd)
                return NULL;
        }
 
-       rtdm_context_lock(context);
+       atomic_inc(&context->close_lock_count);
 
        xnlock_put_irqrestore(&rt_fildes_lock, s);
 
@@ -328,7 +328,7 @@ again:
        }
 
        set_bit(RTDM_CLOSING, &context->context_flags);
-       rtdm_context_lock(context);
+       atomic_inc(&context->close_lock_count);
 
        xnlock_put_irqrestore(&rt_fildes_lock, s);
 
@@ -588,7 +588,11 @@ EXPORT_SYMBOL(rtdm_select_bind);
  * @param[in] context Device context
  *
  * @note rtdm_context_get() automatically increments the lock counter. You
- * only need to call this function in special scenrios.
+ * only need to call this function in special scenarios, e.g. when keeping
+ * additional references to the context structure that have different
+ * lifetimes. Only use rtdm_context_lock() on contexts that are currently
+ * locked via an earlier rtdm_context_get()/rtdm_contex_lock() or while
+ * running a device operation handler.
  *
  * Environments:
  *


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