X-Git-Url: http://git.liburcu.org/?p=urcu.git;a=blobdiff_plain;f=README;fp=README;h=2d29c1d4e1c670800ec808a693f41cca2344ea0c;hp=83330eab1e5ab82cd128dd6c68cdc247f1f272a8;hb=07bd1a22e2ae42578d2a1854de8430cd1af13227;hpb=e85451a199f995091d2f740b6fd0ad2cd8fc2dc7

diff --git a/README b/README
index 83330ea..2d29c1d 100644
--- a/README
+++ b/README
@@ -273,7 +273,20 @@ Interaction with fork()
 	must invoke call_rcu_before_fork() before the fork() and
 	call_rcu_after_fork_parent() after the fork().  The child
 	process must invoke call_rcu_after_fork_child().
-	These three APIs are suitable for passing to pthread_atfork().
+	Even though these three APIs are suitable for passing to
+	pthread_atfork(), use of pthread_atfork() is *STRONGLY
+	DISCOURAGED* for programs calling the glibc memory allocator
+	(malloc(), calloc(), free(), ...) within call_rcu callbacks.
+	This is due to limitations in the way glibc memory allocator
+	handles calls to the memory allocator from concurrent threads
+	while the pthread_atfork() handlers are executing.
+	Combining e.g.:
+	* call to free() from callbacks executed within call_rcu worker
+	  threads,
+	* executing call_rcu atfork handlers within the glibc pthread
+	  atfork mechanism,
+	will sometimes trigger interesting process hangs. This usually
+	hangs on a memory allocator lock within glibc.
 
 Thread Local Storage (TLS)