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.
See http://marc.info/?l=linux-kernel&m=132811276131767&w=2 to check why it might be useful. Signed-off-by: Dmitry Antipov <dmitry.anti...@linaro.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 "khread %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 _______________________________________________ linaro-dev mailing list linaro-dev@lists.linaro.org http://lists.linaro.org/mailman/listinfo/linaro-dev
