Merge branch 'kmemleak' of git://linux-arm.org/linux-2.6

* 'kmemleak' of git://linux-arm.org/linux-2.6:
  kmemleak: Inform kmemleak about pid_hash
  kmemleak: Do not warn if an unknown object is freed
  kmemleak: Do not report new leaked objects if the scanning was stopped
  kmemleak: Slightly change the policy on newly allocated objects
  kmemleak: Do not trigger a scan when reading the debug/kmemleak file
  kmemleak: Simplify the reports logged by the scanning thread
  kmemleak: Enable task stacks scanning by default
  kmemleak: Allow the early log buffer to be configurable.

Documentation/kmemleak.txt

@@ -16,13 +16,17 @@ Usage
 -----
 
 CONFIG_DEBUG_KMEMLEAK in "Kernel hacking" has to be enabled. A kernel
-thread scans the memory every 10 minutes (by default) and prints any new
-unreferenced objects found. To trigger an intermediate scan and display
-all the possible memory leaks:
+thread scans the memory every 10 minutes (by default) and prints the
+number of new unreferenced objects found. To display the details of all
+the possible memory leaks:
 
   # mount -t debugfs nodev /sys/kernel/debug/
   # cat /sys/kernel/debug/kmemleak
 
+To trigger an intermediate memory scan:
+
+  # echo scan > /sys/kernel/debug/kmemleak
+
 Note that the orphan objects are listed in the order they were allocated
 and one object at the beginning of the list may cause other subsequent
 objects to be reported as orphan.
@@ -31,16 +35,21 @@ Memory scanning parameters can be modified at run-time by writing to the
 /sys/kernel/debug/kmemleak file. The following parameters are supported:
 
   off		- disable kmemleak (irreversible)
-  stack=on	- enable the task stacks scanning
+  stack=on	- enable the task stacks scanning (default)
   stack=off	- disable the tasks stacks scanning
-  scan=on	- start the automatic memory scanning thread
+  scan=on	- start the automatic memory scanning thread (default)
   scan=off	- stop the automatic memory scanning thread
-  scan=<secs>	- set the automatic memory scanning period in seconds (0
-		  to disable it)
+  scan=<secs>	- set the automatic memory scanning period in seconds
+		  (default 600, 0 to stop the automatic scanning)
+  scan		- trigger a memory scan
 
 Kmemleak can also be disabled at boot-time by passing "kmemleak=off" on
 the kernel command line.
 
+Memory may be allocated or freed before kmemleak is initialised and
+these actions are stored in an early log buffer. The size of this buffer
+is configured via the CONFIG_DEBUG_KMEMLEAK_EARLY_LOG_SIZE option.
+
 Basic Algorithm
 ---------------
 

kernel/pid.c

@@ -36,6 +36,7 @@
 #include <linux/pid_namespace.h>
 #include <linux/init_task.h>
 #include <linux/syscalls.h>
+#include <linux/kmemleak.h>
 
 #define pid_hashfn(nr, ns)	\
 	hash_long((unsigned long)nr + (unsigned long)ns, pidhash_shift)
@@ -512,6 +513,12 @@ void __init pidhash_init(void)
 	pid_hash = alloc_bootmem(pidhash_size *	sizeof(*(pid_hash)));
 	if (!pid_hash)
 		panic("Could not alloc pidhash!\n");
+	/*
+	 * pid_hash contains references to allocated struct pid objects and it
+	 * must be scanned by kmemleak to avoid false positives.
+	 */
+	kmemleak_alloc(pid_hash, pidhash_size *	sizeof(*(pid_hash)), 0,
+		       GFP_KERNEL);
 	for (i = 0; i < pidhash_size; i++)
 		INIT_HLIST_HEAD(&pid_hash[i]);
 }

lib/Kconfig.debug

@@ -359,6 +359,18 @@ config DEBUG_KMEMLEAK
 	  In order to access the kmemleak file, debugfs needs to be
 	  mounted (usually at /sys/kernel/debug).
 
+config DEBUG_KMEMLEAK_EARLY_LOG_SIZE
+	int "Maximum kmemleak early log entries"
+	depends on DEBUG_KMEMLEAK
+	range 200 2000
+	default 400
+	help
+	  Kmemleak must track all the memory allocations to avoid
+	  reporting false positives. Since memory may be allocated or
+	  freed before kmemleak is initialised, an early log buffer is
+	  used to store these actions. If kmemleak reports "early log
+	  buffer exceeded", please increase this value.
+
 config DEBUG_KMEMLEAK_TEST
 	tristate "Simple test for the kernel memory leak detector"
 	depends on DEBUG_KMEMLEAK