The following commit has been merged into the locking/urgent branch of tip:

Commit-ID: c5cade200ab9a2a3be9e7f32a752c8d86b502ec7 Gitweb: https://git.kernel.org/tip/c5cade200ab9a2a3be9e7f32a752c8d86b502ec7 Author: Thomas Gleixner tglx@linutronix.de AuthorDate: Tue, 19 Jan 2021 15:21:35 +01:00 Committer: Thomas Gleixner tglx@linutronix.de CommitterDate: Tue, 26 Jan 2021 15:10:58 +01:00

futex: Provide and use pi_state_update_owner()

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 --- kernel/futex.c | 66 ++++++++++++++++++++++++------------------------- 1 file changed, 33 insertions(+), 33 deletions(-)

diff --git a/kernel/futex.c b/kernel/futex.c index 5dc8f89..7837f9e 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -763,6 +763,29 @@ 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); + } +} + static void get_pi_state(struct futex_pi_state *pi_state) { WARN_ON_ONCE(!refcount_inc_not_zero(&pi_state->refcount)); @@ -1521,26 +1544,15 @@ static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_pi_state *pi_ ret = -EINVAL; }

- if (ret) - goto out_unlock; - - /* - * This is a point of no return; once we modify the uval there is no - * going back and subsequent operations must not fail. - */ - - raw_spin_lock(&pi_state->owner->pi_lock); - WARN_ON(list_empty(&pi_state->list)); - list_del_init(&pi_state->list); - raw_spin_unlock(&pi_state->owner->pi_lock); - - 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); - - postunlock = __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); + postunlock = __rt_mutex_futex_unlock(&pi_state->pi_mutex, &wake_q); + }

out_unlock: raw_spin_unlock_irq(&pi_state->pi_mutex.wait_lock); @@ -2433,19 +2445,7 @@ retry: * We fixed up user space. Now we need to fix the pi_state * itself. */ - if (pi_state->owner != NULL) { - raw_spin_lock(&pi_state->owner->pi_lock); - WARN_ON(list_empty(&pi_state->list)); - list_del_init(&pi_state->list); - raw_spin_unlock(&pi_state->owner->pi_lock); - } - - pi_state->owner = newowner; - - raw_spin_lock(&newowner->pi_lock); - WARN_ON(!list_empty(&pi_state->list)); - list_add(&pi_state->list, &newowner->pi_state_list); - raw_spin_unlock(&newowner->pi_lock); + pi_state_update_owner(pi_state, newowner); raw_spin_unlock_irq(&pi_state->pi_mutex.wait_lock);

return argowner == current;