Messages in this thread Patch in this message | | | Date | Mon, 10 Apr 2017 11:08:18 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH -v6 13/13] futex: futex_lock_pi() vs PREEMPT_RT_FULL |
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On Fri, Apr 07, 2017 at 07:26:10PM -0700, Darren Hart wrote: > Peter, I presume there will be a v7 with the u32 change and hopefully a couple > text updates?
Well, tglx already committed these here patches, so no -v7. What I can do however is do a follow up patch that fixes some of the in-code things you mentioned.
Something like the below is what I had lying about from your earlier emails; I've not looked to see if there's anything else from your later emails.
--- Subject: futex: Small misc fixes.. From: Peter Zijlstra <peterz@infradead.org> Date: Fri Apr 7 09:04:07 CEST 2017
Feedback from Darren's review.
Reported-by: Darren Hart (VMWare) <dvhart@infradead.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> --- kernel/futex.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-)
--- a/kernel/futex.c +++ b/kernel/futex.c @@ -1025,7 +1025,8 @@ static int attach_to_pi_state(u32 __user struct futex_pi_state **ps) { pid_t pid = uval & FUTEX_TID_MASK; - int ret, uval2; + u32 uval2; + int ret; /* * Userspace might have messed up non-PI and PI futexes [3] @@ -1441,6 +1442,11 @@ static int wake_futex_pi(u32 __user *uad 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); @@ -1452,9 +1458,6 @@ static int wake_futex_pi(u32 __user *uad pi_state->owner = new_owner; raw_spin_unlock(&new_owner->pi_lock); - /* - * We've updated the uservalue, this unlock cannot fail. - */ postunlock = __rt_mutex_futex_unlock(&pi_state->pi_mutex, &wake_q); out_unlock:
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