linux-kernel - kmemleak: Early log buffer exceeded

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Date:	Wed, 15 Jul 2009 22:47:12 +0530
From:	Jaswinder Singh Rajput <jaswinder@...nel.org>
To:	Catalin Marinas <catalin.marinas@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: kmemleak: Early log buffer exceeded

Currently this reporting seems not very impressive and not giving much
useful information :

kmemleak: Early log buffer exceeded
kmemleak: Kernel memory leak detector disabled

It should be something like this because it is an error and this will
disable Kernel memory leak detector :

[    0.000173] ------------[ cut here ]------------
[    0.000186] WARNING: at mm/kmemleak.c:726 log_early+0x39/0xa9()
[    0.000189] Hardware name:         
[    0.000192] Early log buffer exceeded, please increase DEBUG_KMEMLEAK_EARLY_LOG_SIZE
[    0.000195] Modules linked in:
[    0.000202] Pid: 0, comm: swapper Not tainted 2.6.31-rc3 #51
[    0.000206] Call Trace:
[    0.000216]  [<c102cf74>] warn_slowpath_common+0x60/0x90
[    0.000222]  [<c102cfd8>] warn_slowpath_fmt+0x24/0x27
[    0.000227]  [<c109614b>] log_early+0x39/0xa9
[    0.000232]  [<c109682d>] kmemleak_alloc+0x41/0x4c
[    0.000241]  [<c1093b63>] __kmalloc+0xcb/0x153
[    0.000247]  [<c1093c04>] alloc_arraycache+0x19/0x50
[    0.000253]  [<c1093e44>] do_tune_cpucache+0x209/0x35d
[    0.000259]  [<c10940ee>] enable_cpucache+0x58/0x9a
[    0.000267]  [<c14bc6e5>] kmem_cache_init_late+0x21/0xc2
[    0.000274]  [<c14a8a20>] start_kernel+0x1e5/0x2ba
[    0.000280]  [<c14a8340>] i386_start_kernel+0x6a/0x6f
[    0.000380] ---[ end trace 4eaa2a86a8e2da22 ]---
[    0.000384] kmemleak: Kernel memory leak detector disabled

Currently default value of DEBUG_KMEMLEAK_EARLY_LOG_SIZE is 400 which
can be easily exceed-able if debugging is on.

These issues can be fixed like this :

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 12327b2..2eaf8bc 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -362,14 +362,15 @@ config DEBUG_KMEMLEAK
 config DEBUG_KMEMLEAK_EARLY_LOG_SIZE
 	int "Maximum kmemleak early log entries"
 	depends on DEBUG_KMEMLEAK
-	range 200 2000
-	default 400
+	range 256 2048
+	default 512
 	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.
+	  used to store these actions. You need to increase this value,
+	  if kmemleak reports "Early log buffer exceeded, please increase
+	  DEBUG_KMEMLEAK_EARLY_LOG_SIZE".
 
 config DEBUG_KMEMLEAK_TEST
 	tristate "Simple test for the kernel memory leak detector"
diff --git a/mm/kmemleak.c b/mm/kmemleak.c
index 5aabd41..084e927 100644
--- a/mm/kmemleak.c
+++ b/mm/kmemleak.c
@@ -722,7 +722,8 @@ static void log_early(int op_type, const void *ptr, size_t size,
 	struct early_log *log;
 
 	if (crt_early_log >= ARRAY_SIZE(early_log)) {
-		pr_warning("Early log buffer exceeded\n");
+		WARN_ONCE(1, KERN_ERR "Early log buffer exceeded, "
+			  "please increase DEBUG_KMEMLEAK_EARLY_LOG_SIZE\n");
 		kmemleak_disable();
 		return;
 	}

--
JSR

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