search for: yeey

...pxchg(&lock->val, 0, _Q_LOCKED_VAL); if (likely(val == 0)) return; + + /* One more attempt - but if we fail mark it as pending. */ + if (val == _Q_LOCKED_VAL) { + new = Q_LOCKED_VAL |_Q_PENDING_VAL; + + old = atomic_cmpxchg(&lock->val, val, new); + if (old == _Q_LOCKED_VAL) /* YEEY! */ + return; + val = old; + } queue_spin_lock_slowpath(lock, val); } and then the slowpath preserves most of the old logic path (with the pending bit stuff)? > > Signed-off-by: Peter Zijlstra <peterz at infradead.org> > --- > include/asm-generic/qspinlock_types.h |...

...pxchg(&lock->val, 0, _Q_LOCKED_VAL); if (likely(val == 0)) return; + + /* One more attempt - but if we fail mark it as pending. */ + if (val == _Q_LOCKED_VAL) { + new = Q_LOCKED_VAL |_Q_PENDING_VAL; + + old = atomic_cmpxchg(&lock->val, val, new); + if (old == _Q_LOCKED_VAL) /* YEEY! */ + return; + val = old; + } queue_spin_lock_slowpath(lock, val); } and then the slowpath preserves most of the old logic path (with the pending bit stuff)? > > Signed-off-by: Peter Zijlstra <peterz at infradead.org> > --- > include/asm-generic/qspinlock_types.h |...

...> return; > >+ > >+ /* One more attempt - but if we fail mark it as pending. */ > >+ if (val == _Q_LOCKED_VAL) { > >+ new = Q_LOCKED_VAL |_Q_PENDING_VAL; > >+ > >+ old = atomic_cmpxchg(&lock->val, val, new); > >+ if (old == _Q_LOCKED_VAL) /* YEEY! */ > >+ return; > > No, it can leave like that. The unlock path will not clear the pending bit. Err, you are right. It needs to go back in the slowpath. > We are trying to make the fastpath as simple as possible as it may be > inlined. The complexity of the queue spinlock is...

...> return; > >+ > >+ /* One more attempt - but if we fail mark it as pending. */ > >+ if (val == _Q_LOCKED_VAL) { > >+ new = Q_LOCKED_VAL |_Q_PENDING_VAL; > >+ > >+ old = atomic_cmpxchg(&lock->val, val, new); > >+ if (old == _Q_LOCKED_VAL) /* YEEY! */ > >+ return; > > No, it can leave like that. The unlock path will not clear the pending bit. Err, you are right. It needs to go back in the slowpath. > We are trying to make the fastpath as simple as possible as it may be > inlined. The complexity of the queue spinlock is...

...7/06/2014 22:36, Konrad Rzeszutek Wilk ha scritto: > + /* One more attempt - but if we fail mark it as pending. */ > + if (val == _Q_LOCKED_VAL) { > + new = Q_LOCKED_VAL |_Q_PENDING_VAL; > + > + old = atomic_cmpxchg(&lock->val, val, new); > + if (old == _Q_LOCKED_VAL) /* YEEY! */ > + return; > + val = old; > + } Note that Peter's code is in a for(;;) loop: + for (;;) { + /* + * If we observe any contention; queue. + */ + if (val & ~_Q_LOCKED_MASK) + goto queue; + + new = _Q_LOCKED_VAL; + if (val == new) + new |= _Q_PENDING_VAL; + + ol...

...; > >+ /* One more attempt - but if we fail mark it as pending. */ > > >+ if (val == _Q_LOCKED_VAL) { > > >+ new = Q_LOCKED_VAL |_Q_PENDING_VAL; > > >+ > > >+ old = atomic_cmpxchg(&lock->val, val, new); > > >+ if (old == _Q_LOCKED_VAL) /* YEEY! */ > > >+ return; > > > > No, it can leave like that. The unlock path will not clear the pending bit. > > Err, you are right. It needs to go back in the slowpath. What I should have wrote is: if (old == 0) /* YEEY */ return; As that would the same thing as this...

...we fail mark it as pending. */ > >>>> + if (val == _Q_LOCKED_VAL) { > >>>> + new = Q_LOCKED_VAL |_Q_PENDING_VAL; > >>>> + > >>>> + old = atomic_cmpxchg(&lock->val, val, new); > >>>> + if (old == _Q_LOCKED_VAL) /* YEEY! */ > >>>> + return; > >>> No, it can leave like that. The unlock path will not clear the pending bit. > >> Err, you are right. It needs to go back in the slowpath. > > What I should have wrote is: > > > > if (old == 0) /* YEEY */ > &g...

...we fail mark it as pending. */ > >>>> + if (val == _Q_LOCKED_VAL) { > >>>> + new = Q_LOCKED_VAL |_Q_PENDING_VAL; > >>>> + > >>>> + old = atomic_cmpxchg(&lock->val, val, new); > >>>> + if (old == _Q_LOCKED_VAL) /* YEEY! */ > >>>> + return; > >>> No, it can leave like that. The unlock path will not clear the pending bit. > >> Err, you are right. It needs to go back in the slowpath. > > What I should have wrote is: > > > > if (old == 0) /* YEEY */ > &g...

...; if (likely(val == 0)) > return; > + > + /* One more attempt - but if we fail mark it as pending. */ > + if (val == _Q_LOCKED_VAL) { > + new = Q_LOCKED_VAL |_Q_PENDING_VAL; > + > + old = atomic_cmpxchg(&lock->val, val, new); > + if (old == _Q_LOCKED_VAL) /* YEEY! */ > + return; No, it can leave like that. The unlock path will not clear the pending bit. We are trying to make the fastpath as simple as possible as it may be inlined. The complexity of the queue spinlock is in the slowpath. Moreover, an cmpxchg followed immediately followed by another...

Since Waiman seems incapable of doing simple things; here's my take on the paravirt crap. The first few patches are taken from Waiman's latest series, but the virt support is completely new. Its primary aim is to not mess up the native code. I've not stress tested it, but the virt and paravirt (kvm) cases boot on simple smp guests. I've not done Xen, but the patch should be

Since Waiman seems incapable of doing simple things; here's my take on the paravirt crap. The first few patches are taken from Waiman's latest series, but the virt support is completely new. Its primary aim is to not mess up the native code. I've not stress tested it, but the virt and paravirt (kvm) cases boot on simple smp guests. I've not done Xen, but the patch should be

...on (XEN) I/O virtualisation disabled A bit of Googling and I add in "no-amd-iommu-perdev-intremap,no-intremap" That combination looks to blow up the box. If I just do: 'iommu=verbose,debug,no-intremap' it shows that IOMMU is enabled (yeey) (XEN) AMD-Vi: IOMMU 0 Enabled. (XEN) I/O virtualisation enabled and it boots! But if I also add "no-amd-iommu-perdev-intremap" (in addition to no-intremap) it blows up: (XEN) ----[ Xen-4.4-unstable x86_64 debug=y Not tainted ]----...