mm: use do_futex() instead of sys_futex() in mm_release()
sys_futex() is a wrapper to do_futex() which does not modify any values here: - uaddr, val and val3 are kept the same - op is masked with FUTEX_CMD_MASK, but is always set to FUTEX_WAKE. Therefore, val2 is always 0. - as utime is set to NULL, *timeout is NULL This patch is part of a series which removes in-kernel calls to syscalls. On this basis, the syscall entry path can be streamlined. For details, see http://lkml.kernel.org/r/20180325162527.GA17492@light.dominikbrodowski.net Cc: Ingo Molnar <mingo@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Darren Hart <dvhart@infradead.org> Cc: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>
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@ -9,9 +9,6 @@ struct inode;
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struct mm_struct;
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struct task_struct;
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long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout,
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u32 __user *uaddr2, u32 val2, u32 val3);
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extern int
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handle_futex_death(u32 __user *uaddr, struct task_struct *curr, int pi);
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@ -55,6 +52,9 @@ union futex_key {
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#ifdef CONFIG_FUTEX
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extern void exit_robust_list(struct task_struct *curr);
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long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout,
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u32 __user *uaddr2, u32 val2, u32 val3);
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#ifdef CONFIG_HAVE_FUTEX_CMPXCHG
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#define futex_cmpxchg_enabled 1
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#else
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@ -64,6 +64,13 @@ extern int futex_cmpxchg_enabled;
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static inline void exit_robust_list(struct task_struct *curr)
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{
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}
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static inline long do_futex(u32 __user *uaddr, int op, u32 val,
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ktime_t *timeout, u32 __user *uaddr2,
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u32 val2, u32 val3)
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{
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return -EINVAL;
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}
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#endif
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#ifdef CONFIG_FUTEX_PI
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@ -1198,8 +1198,8 @@ void mm_release(struct task_struct *tsk, struct mm_struct *mm)
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* not set up a proper pointer then tough luck.
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*/
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put_user(0, tsk->clear_child_tid);
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sys_futex(tsk->clear_child_tid, FUTEX_WAKE,
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1, NULL, NULL, 0);
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do_futex(tsk->clear_child_tid, FUTEX_WAKE,
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1, NULL, NULL, 0, 0);
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}
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tsk->clear_child_tid = NULL;
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}
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