percpu_counter: add debugobj support (e2852ae8) · Commits · 戴 / test

All percpu counters are linked to a global list on initialization and removed from it on destruction. The list is walked during CPU up/down. If a percpu counter is freed without being properly destroyed, the system will oops only on the next CPU up/down making it pretty nasty to track down. This patch adds debugobj support for percpu counters so that such problems can be found easily. As percpu counters don't make sense on stack and can't be statically initialized, debugobj support is pretty simple. It's initialized and activated on counter initialization, and deactivatd and destroyed on counter destruction. With this patch applied, the bug fixed by commit (shmem: put_super must percpu_counter_destroy) triggers the following warning on tmpfs unmount and the system won't oops on the next cpu up/down operation. ------------[ cut here ]------------ WARNING: at lib/debugobjects.c:259 debug_print_object+0x5c/0x70() Hardware name: Bochs ODEBUG: free active (active state 0) object type: percpu_counter Modules linked in: Pid: 3999, comm: umount Not tainted 2.6.36-rc2-work+ #5 Call Trace: [<ffffffff81083f7f>] warn_slowpath_common+0x7f/0xc0 [<ffffffff81084076>] warn_slowpath_fmt+0x46/0x50 [<ffffffff813b45cc>] debug_print_object+0x5c/0x70 [<ffffffff813b50e5>] debug_check_no_obj_freed+0x125/0x210 [<ffffffff811577d3>] kfree+0xb3/0x2f0 [<ffffffff81132edd>] shmem_put_super+0x1d/0x30 [<ffffffff81162e96>] generic_shutdown_super+0x56/0xe0 [<ffffffff81162f86>] kill_anon_super+0x16/0x60 [<ffffffff81162ff7>] kill_litter_super+0x27/0x30 [<ffffffff81163295>] deactivate_locked_super+0x45/0x60 [<ffffffff81163cfa>] deactivate_super+0x4a/0x70 [<ffffffff8117d446>] mntput_no_expire+0x86/0xe0 [<ffffffff8117df7f>] sys_umount+0x6f/0x360 [<ffffffff8103f01b>] system_call_fastpath+0x16/0x1b ---[ end trace cce2a341ba3611a7 ]--- Signed-off-by:

Tejun Heo <tj@kernel.org> Acked-by: Thomas Gleixner <tglxlinutronix.de> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

lib/Kconfig.debug

+8 −0

Original line number	Diff line number	Diff line
		@@ -317,6 +317,14 @@ config DEBUG_OBJECTS_RCU_HEAD
		help
		Enable this to turn on debugging of RCU list heads (call_rcu() usage).

		config DEBUG_OBJECTS_PERCPU_COUNTER
		bool "Debug percpu counter objects"
		depends on DEBUG_OBJECTS
		help
		If you say Y here, additional code will be inserted into the
		percpu counter routines to track the life time of percpu counter
		objects and validate the percpu counter operations.

		config DEBUG_OBJECTS_ENABLE_DEFAULT
		int "debug_objects bootup default value (0-1)"
		range 0 1

lib/percpu_counter.c

+48 −0

Original line number	Diff line number	Diff line
		@@ -8,10 +8,53 @@
		#include <linux/init.h>
		#include <linux/cpu.h>
		#include <linux/module.h>
		#include <linux/debugobjects.h>

		static LIST_HEAD(percpu_counters);
		static DEFINE_MUTEX(percpu_counters_lock);

		#ifdef CONFIG_DEBUG_OBJECTS_PERCPU_COUNTER

		static struct debug_obj_descr percpu_counter_debug_descr;

		static int percpu_counter_fixup_free(void *addr, enum debug_obj_state state)
		{
		struct percpu_counter *fbc = addr;

		switch (state) {
		case ODEBUG_STATE_ACTIVE:
		percpu_counter_destroy(fbc);
		debug_object_free(fbc, &percpu_counter_debug_descr);
		return 1;
		default:
		return 0;
		}
		}

		static struct debug_obj_descr percpu_counter_debug_descr = {
		.name = "percpu_counter",
		.fixup_free = percpu_counter_fixup_free,
		};

		static inline void debug_percpu_counter_activate(struct percpu_counter *fbc)
		{
		debug_object_init(fbc, &percpu_counter_debug_descr);
		debug_object_activate(fbc, &percpu_counter_debug_descr);
		}

		static inline void debug_percpu_counter_deactivate(struct percpu_counter *fbc)
		{
		debug_object_deactivate(fbc, &percpu_counter_debug_descr);
		debug_object_free(fbc, &percpu_counter_debug_descr);
		}

		#else /* CONFIG_DEBUG_OBJECTS_PERCPU_COUNTER */
		static inline void debug_percpu_counter_activate(struct percpu_counter *fbc)
		{ }
		static inline void debug_percpu_counter_deactivate(struct percpu_counter *fbc)
		{ }
		#endif /* CONFIG_DEBUG_OBJECTS_PERCPU_COUNTER */

		void percpu_counter_set(struct percpu_counter *fbc, s64 amount)
		{
		int cpu;
		@@ -75,6 +118,9 @@ int __percpu_counter_init(struct percpu_counter *fbc, s64 amount,
		fbc->counters = alloc_percpu(s32);
		if (!fbc->counters)
		return -ENOMEM;

		debug_percpu_counter_activate(fbc);

		#ifdef CONFIG_HOTPLUG_CPU
		INIT_LIST_HEAD(&fbc->list);
		mutex_lock(&percpu_counters_lock);
		@@ -90,6 +136,8 @@ void percpu_counter_destroy(struct percpu_counter *fbc)
		if (!fbc->counters)
		return;

		debug_percpu_counter_deactivate(fbc);

		#ifdef CONFIG_HOTPLUG_CPU
		mutex_lock(&percpu_counters_lock);
		list_del(&fbc->list);

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