search for: queue_spin_unlock_wait

...k : Pointer to queue spinlock structure + */ +static __always_inline void queue_spin_unlock(struct qspinlock *lock) +{ + /* + * smp_mb__before_atomic() in order to guarantee release semantics + */ + smp_mb__before_atomic_dec(); + atomic_sub(_Q_LOCKED_VAL, &lock->val); +} +#endif + +/** + * queue_spin_unlock_wait - wait until current lock holder releases the lock + * @lock : Pointer to queue spinlock structure + * + * There is a very slight possibility of live-lock if the lockers keep coming + * and the waiter is just unfortunate enough to not see any unlock state. + */ +static inline void queue_spin_unlock...

...(val), "+m" (*v) > + : "r" (v) > + : "cr0", "xer"); > + > + return val; > +} > + > +void queued_spin_unlock_wait(struct qspinlock *lock) > +{ > + > + u32 val; > + > + smp_mb(); > + > + /* > + * copied from generic queue_spin_unlock_wait with little modification > + */ > + for (;;) { > + /* need _sync, as we might race with another LL/SC in lock()*/ > + val = atomic_read_sync(&lock->val); > + > + if (!val) /* not locked, we're done */ > + goto done; > + > + if (val & _Q_LOCKED_MASK)...

...(val), "+m" (*v) > + : "r" (v) > + : "cr0", "xer"); > + > + return val; > +} > + > +void queued_spin_unlock_wait(struct qspinlock *lock) > +{ > + > + u32 val; > + > + smp_mb(); > + > + /* > + * copied from generic queue_spin_unlock_wait with little modification > + */ > + for (;;) { > + /* need _sync, as we might race with another LL/SC in lock()*/ > + val = atomic_read_sync(&lock->val); > + > + if (!val) /* not locked, we're done */ > + goto done; > + > + if (val & _Q_LOCKED_MASK)...

...; stwcx. %0, 0, %2\n" +" bne- 1b\n" + : "=&r" (val), "+m" (*v) + : "r" (v) + : "cr0", "xer"); + + return val; +} + +void queued_spin_unlock_wait(struct qspinlock *lock) +{ + + u32 val; + + smp_mb(); + + /* + * copied from generic queue_spin_unlock_wait with little modification + */ + for (;;) { + /* need _sync, as we might race with another LL/SC in lock()*/ + val = atomic_read_sync(&lock->val); + + if (!val) /* not locked, we're done */ + goto done; + + if (val & _Q_LOCKED_MASK) /* locked, go wait for unlock */ + break; +...

v13->v14: - Patches 1 & 2: Add queue_spin_unlock_wait() to accommodate commit 78bff1c86 from Oleg Nesterov. - Fix the system hang problem when using PV qspinlock in an over-committed guest due to a racing condition in the pv_set_head_in_tail() function. - Increase the MAYHALT_THRESHOLD from 10 to 1024. - Change kick_cpu into a regular func...

v13->v14: - Patches 1 & 2: Add queue_spin_unlock_wait() to accommodate commit 78bff1c86 from Oleg Nesterov. - Fix the system hang problem when using PV qspinlock in an over-committed guest due to a racing condition in the pv_set_head_in_tail() function. - Increase the MAYHALT_THRESHOLD from 10 to 1024. - Change kick_cpu into a regular func...

...as suggested by David Vrabel <david.vrabel at citrix.com>. - Add benchmarking data for 3.19 kernel to compare the performance of a spinlock heavy test with and without the qspinlock patch under different cpufreq drivers and scaling governors. v13->v14: - Patches 1 & 2: Add queue_spin_unlock_wait() to accommodate commit 78bff1c86 from Oleg Nesterov. - Fix the system hang problem when using PV qspinlock in an over-committed guest due to a racing condition in the pv_set_head_in_tail() function. - Increase the MAYHALT_THRESHOLD from 10 to 1024. - Change kick_cpu into a regular func...

...as suggested by David Vrabel <david.vrabel at citrix.com>. - Add benchmarking data for 3.19 kernel to compare the performance of a spinlock heavy test with and without the qspinlock patch under different cpufreq drivers and scaling governors. v13->v14: - Patches 1 & 2: Add queue_spin_unlock_wait() to accommodate commit 78bff1c86 from Oleg Nesterov. - Fix the system hang problem when using PV qspinlock in an over-committed guest due to a racing condition in the pv_set_head_in_tail() function. - Increase the MAYHALT_THRESHOLD from 10 to 1024. - Change kick_cpu into a regular func...

...as suggested by David Vrabel <david.vrabel at citrix.com>. - Add benchmarking data for 3.19 kernel to compare the performance of a spinlock heavy test with and without the qspinlock patch under different cpufreq drivers and scaling governors. v13->v14: - Patches 1 & 2: Add queue_spin_unlock_wait() to accommodate commit 78bff1c86 from Oleg Nesterov. - Fix the system hang problem when using PV qspinlock in an over-committed guest due to a racing condition in the pv_set_head_in_tail() function. - Increase the MAYHALT_THRESHOLD from 10 to 1024. - Change kick_cpu into a regular func...

...as suggested by David Vrabel <david.vrabel at citrix.com>. - Add benchmarking data for 3.19 kernel to compare the performance of a spinlock heavy test with and without the qspinlock patch under different cpufreq drivers and scaling governors. v13->v14: - Patches 1 & 2: Add queue_spin_unlock_wait() to accommodate commit 78bff1c86 from Oleg Nesterov. - Fix the system hang problem when using PV qspinlock in an over-committed guest due to a racing condition in the pv_set_head_in_tail() function. - Increase the MAYHALT_THRESHOLD from 10 to 1024. - Change kick_cpu into a regular func...

Hi All, this is the fairlock patchset. You can apply them and build successfully. patches are based on linux-next qspinlock can avoid waiter starved issue. It has about the same speed in single-thread and it can be much faster in high contention situations especially when the spinlock is embedded within the data structure to be protected. v7 -> v8: add one patch to drop a function call

Hi All, this is the fairlock patchset. You can apply them and build successfully. patches are based on linux-next qspinlock can avoid waiter starved issue. It has about the same speed in single-thread and it can be much faster in high contention situations especially when the spinlock is embedded within the data structure to be protected. v7 -> v8: add one patch to drop a function call

Hi Waiman, As promised; here is the paravirt stuff I did during the trip to BOS last week. All the !paravirt patches are more or less the same as before (the only real change is the copyright lines in the first patch). The paravirt stuff is 'simple' and KVM only -- the Xen code was a little more convoluted and I've no real way to test that but it should be stright fwd to make work.

Hi Waiman, As promised; here is the paravirt stuff I did during the trip to BOS last week. All the !paravirt patches are more or less the same as before (the only real change is the copyright lines in the first patch). The paravirt stuff is 'simple' and KVM only -- the Xen code was a little more convoluted and I've no real way to test that but it should be stright fwd to make work.

Hi All, this is the fairlock patchset. You can apply them and build successfully. patches are based on linux-next qspinlock can avoid waiter starved issue. It has about the same speed in single-thread and it can be much faster in high contention situations especially when the spinlock is embedded within the data structure to be protected. v8 -> v9: mv qspinlocm config entry to

Hi All, this is the fairlock patchset. You can apply them and build successfully. patches are based on linux-next qspinlock can avoid waiter starved issue. It has about the same speed in single-thread and it can be much faster in high contention situations especially when the spinlock is embedded within the data structure to be protected. v8 -> v9: mv qspinlocm config entry to