futex: Move futex exit handling into futex code

The futex exit handling is #ifdeffed into mm_release() which is not pretty
to begin with. But upcoming changes to address futex exit races need to add
more functionality to this exit code.

Split it out into a function, move it into futex code and make the various
futex exit functions static.

Preparatory only and no functional change.

Folded build fix from Borislav.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20191106224556.049705556@linutronix.de

diff --git a/include/linux/compat.h b/include/linux/compat.h
index 16dafd9f4b862832c00617f7a75b338fb6c25855..c4c389c7e1b4221db8ed4b987ba34e5023425f6d 100644 (file)
--- a/include/linux/compat.h
+++ b/include/linux/compat.h
@@ -410,8 +410,6 @@ struct compat_kexec_segment;
 struct compat_mq_attr;
 struct compat_msgbuf;
 
-extern void compat_exit_robust_list(struct task_struct *curr);
-
 #define BITS_PER_COMPAT_LONG    (8*sizeof(compat_long_t))
 
 #define BITS_TO_COMPAT_LONGS(bits) DIV_ROUND_UP(bits, BITS_PER_COMPAT_LONG)

diff --git a/include/linux/futex.h b/include/linux/futex.h
index ccaef0097785b84545d95ef8543406ee3ff01231..d6ed11c51a8ed4339f5f840f476261bcdc120e3d 100644 (file)
--- a/include/linux/futex.h
+++ b/include/linux/futex.h
@@ -2,7 +2,9 @@
 #ifndef _LINUX_FUTEX_H
 #define _LINUX_FUTEX_H
 
+#include <linux/sched.h>
 #include <linux/ktime.h>
+
 #include <uapi/linux/futex.h>
 
 struct inode;
@@ -48,15 +50,24 @@ union futex_key {
 #define FUTEX_KEY_INIT (union futex_key) { .both = { .ptr = NULL } }
 
 #ifdef CONFIG_FUTEX
-extern void exit_robust_list(struct task_struct *curr);
 
-long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout,
-             u32 __user *uaddr2, u32 val2, u32 val3);
-#else
-static inline void exit_robust_list(struct task_struct *curr)
+static inline void futex_init_task(struct task_struct *tsk)
 {
+       tsk->robust_list = NULL;
+#ifdef CONFIG_COMPAT
+       tsk->compat_robust_list = NULL;
+#endif
+       INIT_LIST_HEAD(&tsk->pi_state_list);
+       tsk->pi_state_cache = NULL;
 }
 
+void futex_mm_release(struct task_struct *tsk);
+
+long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout,
+             u32 __user *uaddr2, u32 val2, u32 val3);
+#else
+static inline void futex_init_task(struct task_struct *tsk) { }
+static inline void futex_mm_release(struct task_struct *tsk) { }
 static inline long do_futex(u32 __user *uaddr, int op, u32 val,
                            ktime_t *timeout, u32 __user *uaddr2,
                            u32 val2, u32 val3)
@@ -65,12 +76,4 @@ static inline long do_futex(u32 __user *uaddr, int op, u32 val,
 }
 #endif
 
-#ifdef CONFIG_FUTEX_PI
-extern void exit_pi_state_list(struct task_struct *curr);
-#else
-static inline void exit_pi_state_list(struct task_struct *curr)
-{
-}
-#endif
-
 #endif

diff --git a/kernel/fork.c b/kernel/fork.c
index bcdf5312521036486b7613e7499d7174e62526c6..bd7c218691d4e22d4727f572191cdf3f3a058013 100644 (file)
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1286,20 +1286,7 @@ static int wait_for_vfork_done(struct task_struct *child,
 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
 {
        /* Get rid of any futexes when releasing the mm */
-#ifdef CONFIG_FUTEX
-       if (unlikely(tsk->robust_list)) {
-               exit_robust_list(tsk);
-               tsk->robust_list = NULL;
-       }
-#ifdef CONFIG_COMPAT
-       if (unlikely(tsk->compat_robust_list)) {
-               compat_exit_robust_list(tsk);
-               tsk->compat_robust_list = NULL;
-       }
-#endif
-       if (unlikely(!list_empty(&tsk->pi_state_list)))
-               exit_pi_state_list(tsk);
-#endif
+       futex_mm_release(tsk);
 
        uprobe_free_utask(tsk);
 
@@ -2062,14 +2049,8 @@ static __latent_entropy struct task_struct *copy_process(
 #ifdef CONFIG_BLOCK
        p->plug = NULL;
 #endif
-#ifdef CONFIG_FUTEX
-       p->robust_list = NULL;
-#ifdef CONFIG_COMPAT
-       p->compat_robust_list = NULL;
-#endif
-       INIT_LIST_HEAD(&p->pi_state_list);
-       p->pi_state_cache = NULL;
-#endif
+       futex_init_task(p);
+
        /*
         * sigaltstack should be cleared when sharing the same VM
         */

diff --git a/kernel/futex.c b/kernel/futex.c
index 49eaf5be851a62d8697d84052d8cec7141b86aef..f8f00d47c821df56a2254e92752146862b92c024 100644 (file)
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -325,6 +325,12 @@ static inline bool should_fail_futex(bool fshared)
 }
 #endif /* CONFIG_FAIL_FUTEX */
 
+#ifdef CONFIG_COMPAT
+static void compat_exit_robust_list(struct task_struct *curr);
+#else
+static inline void compat_exit_robust_list(struct task_struct *curr) { }
+#endif
+
 static inline void futex_get_mm(union futex_key *key)
 {
        mmgrab(key->private.mm);
@@ -890,7 +896,7 @@ static void put_pi_state(struct futex_pi_state *pi_state)
  * Kernel cleans up PI-state, but userspace is likely hosed.
  * (Robust-futex cleanup is separate and might save the day for userspace.)
  */
-void exit_pi_state_list(struct task_struct *curr)
+static void exit_pi_state_list(struct task_struct *curr)
 {
        struct list_head *next, *head = &curr->pi_state_list;
        struct futex_pi_state *pi_state;
@@ -960,7 +966,8 @@ void exit_pi_state_list(struct task_struct *curr)
        }
        raw_spin_unlock_irq(&curr->pi_lock);
 }
-
+#else
+static inline void exit_pi_state_list(struct task_struct *curr) { }
 #endif
 
 /*
@@ -3588,7 +3595,7 @@ static inline int fetch_robust_entry(struct robust_list __user **entry,
  *
  * We silently return on any sign of list-walking problem.
  */
-void exit_robust_list(struct task_struct *curr)
+static void exit_robust_list(struct task_struct *curr)
 {
        struct robust_list_head __user *head = curr->robust_list;
        struct robust_list __user *entry, *next_entry, *pending;
@@ -3653,6 +3660,24 @@ void exit_robust_list(struct task_struct *curr)
        }
 }
 
+void futex_mm_release(struct task_struct *tsk)
+{
+       if (unlikely(tsk->robust_list)) {
+               exit_robust_list(tsk);
+               tsk->robust_list = NULL;
+       }
+
+#ifdef CONFIG_COMPAT
+       if (unlikely(tsk->compat_robust_list)) {
+               compat_exit_robust_list(tsk);
+               tsk->compat_robust_list = NULL;
+       }
+#endif
+
+       if (unlikely(!list_empty(&tsk->pi_state_list)))
+               exit_pi_state_list(tsk);
+}
+
 long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout,
                u32 __user *uaddr2, u32 val2, u32 val3)
 {
@@ -3780,7 +3805,7 @@ static void __user *futex_uaddr(struct robust_list __user *entry,
  *
  * We silently return on any sign of list-walking problem.
  */
-void compat_exit_robust_list(struct task_struct *curr)
+static void compat_exit_robust_list(struct task_struct *curr)
 {
        struct compat_robust_list_head __user *head = curr->compat_robust_list;
        struct robust_list __user *entry, *next_entry, *pending;