kernel, oom: fix potential pgd_lock deadlock from __mmdrop

[cascardo/linux.git] / kernel / fork.c

diff --git a/kernel/fork.c b/kernel/fork.c
index c060c7e..5650e35 100644 (file)
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -359,6 +359,12 @@ static inline void free_signal_struct(struct signal_struct *sig)
 {
        taskstats_tgid_free(sig);
        sched_autogroup_exit(sig);
+       /*
+        * __mmdrop is not safe to call from softirq context on x86 due to
+        * pgd_dtor so postpone it to the async context
+        */
+       if (sig->oom_mm)
+               mmdrop_async(sig->oom_mm);
        kmem_cache_free(signal_cachep, sig);
 }
 
@@ -418,6 +424,7 @@ int arch_task_struct_size __read_mostly;
 
 void __init fork_init(void)
 {
+       int i;
 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
 #ifndef ARCH_MIN_TASKALIGN
 #define ARCH_MIN_TASKALIGN     L1_CACHE_BYTES
@@ -437,6 +444,10 @@ void __init fork_init(void)
        init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
        init_task.signal->rlim[RLIMIT_SIGPENDING] =
                init_task.signal->rlim[RLIMIT_NPROC];
+
+       for (i = 0; i < UCOUNT_COUNTS; i++) {
+               init_user_ns.ucount_max[i] = max_threads/2;
+       }
 }
 
 int __weak arch_dup_task_struct(struct task_struct *dst,