diff options
author | Lee Jones <lee.jones@linaro.org> | 2021-02-04 17:28:59 +0000 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2021-02-10 09:07:25 +0100 |
commit | 34c8e1c2c025b8c3eefb43fbcec2699841f0d153 (patch) | |
tree | b82e97aa318c5e07211a41636a9152efb0b2f8e4 /kernel | |
parent | 3edf5f2ad6652c4e3e6c1eaf4d64be7cf516b1b5 (diff) |
futex: Provide and use pi_state_update_owner()
From: Thomas Gleixner <tglx@linutronix.de>
[ Upstream commit c5cade200ab9a2a3be9e7f32a752c8d86b502ec7 ]
Updating pi_state::owner is done at several places with the same
code. Provide a function for it and use that at the obvious places.
This is also a preparation for a bug fix to avoid yet another copy of the
same code or alternatively introducing a completely unpenetratable mess of
gotos.
Originally-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: stable@vger.kernel.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'kernel')
-rw-r--r-- | kernel/futex.c | 64 |
1 files changed, 33 insertions, 31 deletions
diff --git a/kernel/futex.c b/kernel/futex.c index a247942d6979..1390ffa874a6 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -835,6 +835,29 @@ static struct futex_pi_state * alloc_pi_state(void) return pi_state; } +static void pi_state_update_owner(struct futex_pi_state *pi_state, + struct task_struct *new_owner) +{ + struct task_struct *old_owner = pi_state->owner; + + lockdep_assert_held(&pi_state->pi_mutex.wait_lock); + + if (old_owner) { + raw_spin_lock(&old_owner->pi_lock); + WARN_ON(list_empty(&pi_state->list)); + list_del_init(&pi_state->list); + raw_spin_unlock(&old_owner->pi_lock); + } + + if (new_owner) { + raw_spin_lock(&new_owner->pi_lock); + WARN_ON(!list_empty(&pi_state->list)); + list_add(&pi_state->list, &new_owner->pi_state_list); + pi_state->owner = new_owner; + raw_spin_unlock(&new_owner->pi_lock); + } +} + /* * Must be called with the hb lock held. */ @@ -1427,26 +1450,16 @@ static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *this, else ret = -EINVAL; } - if (ret) { - raw_spin_unlock(&pi_state->pi_mutex.wait_lock); - return ret; - } - - raw_spin_lock_irq(&pi_state->owner->pi_lock); - WARN_ON(list_empty(&pi_state->list)); - list_del_init(&pi_state->list); - raw_spin_unlock_irq(&pi_state->owner->pi_lock); - raw_spin_lock_irq(&new_owner->pi_lock); - WARN_ON(!list_empty(&pi_state->list)); - list_add(&pi_state->list, &new_owner->pi_state_list); - pi_state->owner = new_owner; - raw_spin_unlock_irq(&new_owner->pi_lock); - - /* - * We've updated the uservalue, this unlock cannot fail. - */ - deboost = __rt_mutex_futex_unlock(&pi_state->pi_mutex, &wake_q); + if (!ret) { + /* + * This is a point of no return; once we modified the uval + * there is no going back and subsequent operations must + * not fail. + */ + pi_state_update_owner(pi_state, new_owner); + deboost = __rt_mutex_futex_unlock(&pi_state->pi_mutex, &wake_q); + } raw_spin_unlock_irq(&pi_state->pi_mutex.wait_lock); spin_unlock(&hb->lock); @@ -2318,19 +2331,8 @@ retry: * We fixed up user space. Now we need to fix the pi_state * itself. */ - if (pi_state->owner != NULL) { - raw_spin_lock_irq(&pi_state->owner->pi_lock); - WARN_ON(list_empty(&pi_state->list)); - list_del_init(&pi_state->list); - raw_spin_unlock_irq(&pi_state->owner->pi_lock); - } - - pi_state->owner = newowner; + pi_state_update_owner(pi_state, newowner); - raw_spin_lock_irq(&newowner->pi_lock); - WARN_ON(!list_empty(&pi_state->list)); - list_add(&pi_state->list, &newowner->pi_state_list); - raw_spin_unlock_irq(&newowner->pi_lock); return 0; /* |