Messages in this thread Patch in this message | | | From | Mandeep Singh Baines <> | Subject | [PATCH v6] lockdep: check that no locks held at freeze time | Date | Thu, 21 Feb 2013 08:51:41 -0800 |
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We shouldn't try_to_freeze if locks are held. Holding a lock can cause a deadlock if the lock is later acquired in the suspend or hibernate path (e.g. by dpm). Holding a lock can also cause a deadlock in the case of cgroup_freezer if a lock is held inside a frozen cgroup that is later acquired by a process outside that group.
Changes since v1: * LKML: <20130215111635.GA26955@gmail.com> Ingo Molnar * Added a msg string that gets passed in. * LKML: <20130215154449.GD30829@redhat.com> Oleg Nesterov * Check PF_NOFREEZE in try_to_freeze(). Changes since v2: * LKML: <20130216170605.GC4910@redhat.com> Oleg Nesterovw * Avoid unnecessary PF_NOFREEZE check when !CONFIG_LOCKDEP. * Mandeep Singh Baines * Generalize an exit specific printk. Changes since v3: * LKML: <20130220223013.GA15760@redhat.com> Oleg Nesterovw * Remove stale vfork comment from commit message. Changes since v4: * LKML: <20130220152446.a65ff84f.akpm@linux-foundation.org> Andrew Morton * Remove tsk param since tsk is always current. * Remove msg param, dump_stack() should tell us all we need to know. Changes since v5: * LKML: <3556388.kjl7k6r8W6@vostro.rjw.lan> Rafael J. Wysocki * Updated changelog explaining why we can't freeze with locks held.
Signed-off-by: Mandeep Singh Baines <msb@chromium.org> CC: Ingo Molnar <mingo@redhat.com> CC: Oleg Nesterov <oleg@redhat.com> CC: Tejun Heo <tj@kernel.org> CC: Andrew Morton <akpm@linux-foundation.org> CC: Rafael J. Wysocki <rjw@sisk.pl> --- include/linux/debug_locks.h | 4 ++-- include/linux/freezer.h | 3 +++ kernel/exit.c | 2 +- kernel/lockdep.c | 16 +++++++--------- 4 files changed, 13 insertions(+), 12 deletions(-)
diff --git a/include/linux/debug_locks.h b/include/linux/debug_locks.h index 3bd46f7..a975de1 100644 --- a/include/linux/debug_locks.h +++ b/include/linux/debug_locks.h @@ -51,7 +51,7 @@ struct task_struct; extern void debug_show_all_locks(void); extern void debug_show_held_locks(struct task_struct *task); extern void debug_check_no_locks_freed(const void *from, unsigned long len); -extern void debug_check_no_locks_held(struct task_struct *task); +extern void debug_check_no_locks_held(void); #else static inline void debug_show_all_locks(void) { @@ -67,7 +67,7 @@ debug_check_no_locks_freed(const void *from, unsigned long len) } static inline void -debug_check_no_locks_held(struct task_struct *task) +debug_check_no_locks_held(void) { } #endif diff --git a/include/linux/freezer.h b/include/linux/freezer.h index e4238ce..c5bd118 100644 --- a/include/linux/freezer.h +++ b/include/linux/freezer.h @@ -3,6 +3,7 @@ #ifndef FREEZER_H_INCLUDED #define FREEZER_H_INCLUDED +#include <linux/debug_locks.h> #include <linux/sched.h> #include <linux/wait.h> #include <linux/atomic.h> @@ -43,6 +44,8 @@ extern void thaw_kernel_threads(void); static inline bool try_to_freeze(void) { + if (!(current->flags & PF_NOFREEZE)) + debug_check_no_locks_held(); might_sleep(); if (likely(!freezing(current))) return false; diff --git a/kernel/exit.c b/kernel/exit.c index b4df219..aff5bdb 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -833,7 +833,7 @@ void do_exit(long code) /* * Make sure we are holding no locks: */ - debug_check_no_locks_held(tsk); + debug_check_no_locks_held(); /* * We can do this unlocked here. The futex code uses this flag * just to verify whether the pi state cleanup has been done diff --git a/kernel/lockdep.c b/kernel/lockdep.c index 7981e5b..8e28f56 100644 --- a/kernel/lockdep.c +++ b/kernel/lockdep.c @@ -4083,7 +4083,7 @@ void debug_check_no_locks_freed(const void *mem_from, unsigned long mem_len) } EXPORT_SYMBOL_GPL(debug_check_no_locks_freed); -static void print_held_locks_bug(struct task_struct *curr) +static void print_held_locks_bug(void) { if (!debug_locks_off()) return; @@ -4092,21 +4092,19 @@ static void print_held_locks_bug(struct task_struct *curr) printk("\n"); printk("=====================================\n"); - printk("[ BUG: lock held at task exit time! ]\n"); + printk("[ BUG: %s/%d still has locks held! ]\n", + current->comm, task_pid_nr(current)); print_kernel_ident(); printk("-------------------------------------\n"); - printk("%s/%d is exiting with locks still held!\n", - curr->comm, task_pid_nr(curr)); - lockdep_print_held_locks(curr); - + lockdep_print_held_locks(current); printk("\nstack backtrace:\n"); dump_stack(); } -void debug_check_no_locks_held(struct task_struct *task) +void debug_check_no_locks_held(void) { - if (unlikely(task->lockdep_depth > 0)) - print_held_locks_bug(task); + if (unlikely(current->lockdep_depth > 0)) + print_held_locks_bug(); } void debug_show_all_locks(void) -- 1.7.12.4
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