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Message-Id: <1330419863-3508-1-git-send-email-dmitry.antipov@linaro.org>
Date: Tue, 28 Feb 2012 13:04:23 +0400
From: Dmitry Antipov <dmitry.antipov@...aro.org>
To: Rusty Russell <rusty.russell@...aro.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
linux-kernel@...r.kernel.org, linaro-dev@...ts.linaro.org,
patches@...aro.org, Dmitry Antipov <dmitry.antipov@...aro.org>
Subject: [RFC PATCH] module: debugging check for runaway kthreads
Debugging option CONFIG_MODULE_KTHREAD_CHECK provides a way to check
whether all kernel threads created by the module and have used module
code as a thread worker function are really exited when the module is
unloaded. The following pseudo-code contains example of an error which
is likely to be catched with this debugging check:
static struct task_struct *tsk;
static DECLARE_COMPLETION(done);
static void *func(void *unused)
{
while (!kthread_should_stop())
real_work();
complete(&done);
}
static int __init modinit(void)
{
tsk = kthread_run(func, NULL, "func");
return IS_ERR(tsk) ? PTR_ERR(tsk) : 0;
}
static void __exit modexit(void)
{
wait_for_completion(&done);
}
Signed-off-by: Dmitry Antipov <dmitry.antipov@...aro.org>
---
include/linux/kthread.h | 5 +++++
init/Kconfig | 9 +++++++++
kernel/kthread.c | 24 ++++++++++++++++++++++++
kernel/module.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
4 files changed, 83 insertions(+), 0 deletions(-)
diff --git a/include/linux/kthread.h b/include/linux/kthread.h
index 0714b24..33897c3 100644
--- a/include/linux/kthread.h
+++ b/include/linux/kthread.h
@@ -13,6 +13,11 @@ struct task_struct *kthread_create_on_node(int (*threadfn)(void *data),
#define kthread_create(threadfn, data, namefmt, arg...) \
kthread_create_on_node(threadfn, data, -1, namefmt, ##arg)
+#ifdef CONFIG_MODULE_KTHREAD_CHECK
+unsigned long get_kthread_func(struct task_struct *tsk);
+#else
+#define get_kthread_func(tsk, addr, mod) (0)
+#endif
/**
* kthread_run - create and wake a thread.
diff --git a/init/Kconfig b/init/Kconfig
index 3f42cd6..fa7c6e0 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1397,6 +1397,15 @@ config MODULE_FORCE_UNLOAD
rmmod). This is mainly for kernel developers and desperate users.
If unsure, say N.
+config MODULE_KTHREAD_CHECK
+ bool "Check for runaway kernel threads at module unload"
+ depends on MODULE_UNLOAD && EXPERIMENTAL && DEBUG_KERNEL
+ help
+ This option allows you to check whether all kernel threads created
+ by the module and have used module code as a thread worker function
+ are really exited when the module is unloaded. This is mainly for
+ module developers. If insure, say N.
+
config MODVERSIONS
bool "Module versioning support"
help
diff --git a/kernel/kthread.c b/kernel/kthread.c
index 3d3de63..5c53817 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -38,6 +38,9 @@ struct kthread_create_info
struct kthread {
int should_stop;
+#ifdef CONFIG_MODULE_KTHREAD_CHECK
+ void *fn;
+#endif
void *data;
struct completion exited;
};
@@ -45,6 +48,24 @@ struct kthread {
#define to_kthread(tsk) \
container_of((tsk)->vfork_done, struct kthread, exited)
+#ifdef CONFIG_MODULE_KTHREAD_CHECK
+
+unsigned long get_kthread_func(struct task_struct *tsk)
+{
+ struct kthread *kt;
+ unsigned long addr;
+
+ get_task_struct(tsk);
+ BUG_ON(!(tsk->flags & PF_KTHREAD));
+ kt = to_kthread(tsk);
+ barrier();
+ addr = tsk->vfork_done ? (unsigned long)kt->fn : 0UL;
+ put_task_struct(tsk);
+ return addr;
+}
+
+#endif /* CONFIG_MODULE_KTHREAD_CHECK */
+
/**
* kthread_should_stop - should this kthread return now?
*
@@ -106,6 +127,9 @@ static int kthread(void *_create)
int ret;
self.should_stop = 0;
+#ifdef CONFIG_MODULE_KTHREAD_CHECK
+ self.fn = threadfn;
+#endif
self.data = data;
init_completion(&self.exited);
current->vfork_done = &self.exited;
diff --git a/kernel/module.c b/kernel/module.c
index 2c93276..fe6637b 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -45,6 +45,7 @@
#include <linux/string.h>
#include <linux/mutex.h>
#include <linux/rculist.h>
+#include <linux/kthread.h>
#include <asm/uaccess.h>
#include <asm/cacheflush.h>
#include <asm/mmu_context.h>
@@ -764,6 +765,49 @@ static void wait_for_zero_refcount(struct module *mod)
mutex_lock(&module_mutex);
}
+#ifdef CONFIG_KALLSYMS
+static const char *get_ksymbol(struct module *mod, unsigned long addr,
+ unsigned long *size, unsigned long *offset);
+#else
+#define get_ksymbol(mod, addr, size, offset) NULL
+#endif
+
+#ifdef CONFIG_MODULE_KTHREAD_CHECK
+
+static void check_kthreads(struct module *mod)
+{
+ unsigned long flags;
+ struct task_struct *g, *p;
+
+ read_lock_irqsave(&tasklist_lock, flags);
+ do_each_thread(g, p) {
+ const char *name;
+ unsigned long addr, offset, size;
+
+ /* Note kthreadd is special. Other kthreads should
+ have their 'struct kthread' on the stack until
+ do_exit() calls schedule() for the last time. */
+ if (p->mm || p == kthreadd_task)
+ continue;
+
+ addr = get_kthread_func(p);
+ if (__module_text_address(addr) == mod) {
+ name = get_ksymbol(mod, addr, &size, &offset);
+ printk(KERN_WARNING "kthread %p[%s:%d] running "
+ "0x%lx(%s) is still alive, fix module %s, "
+ "crash possible\n", p, p->comm, p->pid, addr,
+ (name ? name : "<unknown>"), mod->name);
+ }
+ } while_each_thread(g, p);
+ read_unlock_irqrestore(&tasklist_lock, flags);
+}
+
+#else
+
+#define check_kthreads(mod) do { } while (0)
+
+#endif /* CONFIG_MODULE_KTHREAD_CHECK */
+
SYSCALL_DEFINE2(delete_module, const char __user *, name_user,
unsigned int, flags)
{
@@ -831,6 +875,7 @@ SYSCALL_DEFINE2(delete_module, const char __user *, name_user,
blocking_notifier_call_chain(&module_notify_list,
MODULE_STATE_GOING, mod);
async_synchronize_full();
+ check_kthreads(mod);
/* Store the name of the last unloaded module for diagnostic purposes */
strlcpy(last_unloaded_module, mod->name, sizeof(last_unloaded_module));
--
1.7.7.6
--
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