Changeset 497bd656 in mainline

Timestamp:

2012-11-16T14:49:21Z (11 years ago)

Author:

Adam Hraska <adam.hraska+hos@…>

Branches:

lfn, master, serial, ticket/834-toolchain-update, topic/msim-upgrade, topic/simplify-dev-export

Children:

9fe9d296

Parents:

4f5e1c7c

Message:

Fix: averted a possible deadlock in condvar_wait_timeout() (eg when a thread has been interrupted and calls the function concurrently with another thread contending the mutex). Locking discipline: lock the mutex before the waitq.

File:

• kernel/generic/src/synch/condvar.c (modified) (4 diffs)

kernel/generic/src/synch/condvar.c

@@ -91 +91 @@
 
         ipl = waitq_sleep_prepare(&cv->wq);
+        /* Unlock only after the waitq is locked so we don't miss a wakeup. */
         mutex_unlock(mtx);
 
@@ -96 +97 @@
         rc = waitq_sleep_timeout_unsafe(&cv->wq, usec, flags);
 
+        waitq_sleep_finish(&cv->wq, rc, ipl);
+        /* Lock only after releasing the waitq to avoid a possible deadlock. */
         mutex_lock(mtx);
-        waitq_sleep_finish(&cv->wq, rc, ipl);
 
         return rc;
@@ -128 +130 @@
         ipl = waitq_sleep_prepare(&cv->wq);
 
+        /* Unlock only after the waitq is locked so we don't miss a wakeup. */
         spinlock_unlock(lock);
 
@@ -134 +137 @@
 
         waitq_sleep_finish(&cv->wq, rc, ipl);
-        
+        /* Lock only after releasing the waitq to avoid a possible deadlock. */
         spinlock_lock(lock);