[commit: ghc] master: LibdwPool: Use poolTryTake (1712a9e)

[git at git.haskell.org]

Repository : ssh://git@git.haskell.org/ghc

On branch  : master
Link       : http://ghc.haskell.org/trac/ghc/changeset/1712a9ed333dfa2fc9ce7d55acab08a8d278fb5b/ghc

>---------------------------------------------------------------

commit 1712a9ed333dfa2fc9ce7d55acab08a8d278fb5b
Author: Ben Gamari <ben at smart-cactus.org>
Date:   Thu Nov 26 12:02:47 2015 +0100

    LibdwPool: Use poolTryTake


>---------------------------------------------------------------

1712a9ed333dfa2fc9ce7d55acab08a8d278fb5b
 rts/LibdwPool.c | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/rts/LibdwPool.c b/rts/LibdwPool.c
index f625c0f..b0de8ac 100644
--- a/rts/LibdwPool.c
+++ b/rts/LibdwPool.c
@@ -16,6 +16,23 @@
 
 #include "Pool.h"
 
+/*
+ * Note [libdw session pool]
+ * ~~~~~~~~~~~~~~~~~~~~~~~~~
+ *
+ * Building a libdw session requires a number of rather expensive steps,
+ *
+ *   - Examine the object files mapped into the address space
+ *   - Find them on disk
+ *   - Open them and map their debugging information
+ *   - Build various index structures necessary for quick lookup
+ *
+ * The time to setup a session can be several milliseconds. In order to avoid
+ * incurring this cost too often, we keep a pool of warm sessions around which
+ * can be shared between capabilities.
+ *
+ */
+
 static Pool *pool = NULL;
 static nat pool_size = 10; // TODO
 
@@ -26,7 +43,7 @@ void libdwPoolInit(void) {
 }
 
 LibdwSession *libdwPoolTake(void) {
-    return poolTake(pool);
+    return poolTryTake(pool);
 }
 
 void libdwPoolRelease(LibdwSession *sess) {