Module: xenomai-2.5
Branch: master
Commit: b52d6a13471e15f4b8ad51f0aa57d9a090950dcf
URL:
http://git.xenomai.org/?p=xenomai-2.5.git;a=commit;h=b52d6a13471e15f4b8ad51f0aa57d9a090950dcf
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 d68f542..3fc9071 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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