search for: pv_cpu_act

...ad will + * be halted after 2*QSPIN_THRESHOLD whereas the other nodes will be + * halted after QSPIN_THRESHOLD. + */ +#define QSPIN_THRESHOLD (1U<<14) + +/* + * PV macros + */ +#define PV_SET_VAR(type, var, val) type var = val +#define PV_VAR(var) var + +/* + * CPU state flags + */ +#define PV_CPU_ACTIVE 1 /* This CPU is active */ +#define PV_CPU_KICKING 2 /* This CPU is kicking other CPU */ +#define PV_CPU_KICKED 3 /* This CPU is being kicked */ +#define PV_CPU_HALTED -1 /* This CPU is halted */ + +/* + * Additional fields to be added to the qnode structure + */ +#if CONFIG_NR_CPUS >=...

...e head (in pv_halt_check). + * See the comments on those functions to see how the races are being + * addressed. + */ + +/* + * Spin threshold for queue spinlock + */ +#define QSPIN_THRESHOLD (1U<<14) +#define MAYHALT_THRESHOLD (QSPIN_THRESHOLD - 0x10) + +/* + * CPU state flags + */ +#define PV_CPU_ACTIVE 1 /* This CPU is active */ +#define PV_CPU_KICKED 2 /* This CPU is being kicked */ +#define PV_CPU_HALTED -1 /* This CPU is halted */ + +/* + * Additional fields to be added to the queue node structure + * + * The size of the mcs_spinlock structure is 16 bytes for x64 and 12 bytes + * for...

...= cmpxchg(&qlock->lock, > _QSPINLOCK_LOCKED, > _QSPINLOCK_LOCKED_SLOWPATH); > if (lockval == 0) { > /* > * Can exit now as the lock is free > */ > ACCESS_ONCE(pv->cpustate) = PV_CPU_ACTIVE; > *count = 0; > return; > } > __queue_hibernate(); > > Nothing protects from writing qlock->lock before pv->cpustate is read, > leading to this: > > Lock holder Waiter > -----------------------------...

...= cmpxchg(&qlock->lock, > _QSPINLOCK_LOCKED, > _QSPINLOCK_LOCKED_SLOWPATH); > if (lockval == 0) { > /* > * Can exit now as the lock is free > */ > ACCESS_ONCE(pv->cpustate) = PV_CPU_ACTIVE; > *count = 0; > return; > } > __queue_hibernate(); > > Nothing protects from writing qlock->lock before pv->cpustate is read, > leading to this: > > Lock holder Waiter > -----------------------------...

On 12/03/14 18:54, Waiman Long wrote: > This patch adds para-virtualization support to the queue spinlock in > the same way as was done in the PV ticket lock code. In essence, the > lock waiters will spin for a specified number of times (QSPIN_THRESHOLD > = 2^14) and then halted itself. The queue head waiter will spins > 2*QSPIN_THRESHOLD times before halting itself. When it has

On 12/03/14 18:54, Waiman Long wrote: > This patch adds para-virtualization support to the queue spinlock in > the same way as was done in the PV ticket lock code. In essence, the > lock waiters will spin for a specified number of times (QSPIN_THRESHOLD > = 2^14) and then halted itself. The queue head waiter will spins > 2*QSPIN_THRESHOLD times before halting itself. When it has

...e previous queue head (in pv_wait_check). + * + * See the comments on those functions to see how the races are being + * addressed. + */ + +/* + * Spin thresholds for queue spinlock + */ +#define QSPIN_THRESHOLD SPIN_THRESHOLD +#define MAYHALT_THRESHOLD 0x10 + +/* + * CPU state flags + */ +#define PV_CPU_ACTIVE 1 /* This CPU is active */ +#define PV_CPU_KICKED 2 /* This CPU is being kicked */ +#define PV_CPU_HALTED -1 /* This CPU is halted */ + +/* + * Special head node pointer value + */ +#define PV_INVALID_HEAD NULL + +/* + * Additional fields to be added to the queue node structure + * + * Th...

...e previous queue head (in pv_wait_check). + * + * See the comments on those functions to see how the races are being + * addressed. + */ + +/* + * Spin thresholds for queue spinlock + */ +#define QSPIN_THRESHOLD SPIN_THRESHOLD +#define MAYHALT_THRESHOLD 0x10 + +/* + * CPU state flags + */ +#define PV_CPU_ACTIVE 1 /* This CPU is active */ +#define PV_CPU_KICKED 2 /* This CPU is being kicked */ +#define PV_CPU_HALTED -1 /* This CPU is halted */ + +/* + * Special head node pointer value + */ +#define PV_INVALID_HEAD NULL + +/* + * Additional fields to be added to the queue node structure + * + * Th...

...----------------- // pv_head_spin_check ACCESS_ONCE(pv->cpustate) = PV_CPU_HALTED; lockval = cmpxchg(&qlock->lock, _QSPINLOCK_LOCKED, _QSPINLOCK_LOCKED_SLOWPATH); if (lockval == 0) { /* * Can exit now as the lock is free */ ACCESS_ONCE(pv->cpustate) = PV_CPU_ACTIVE; *count = 0; return; } __queue_hibernate(); Nothing protects from writing qlock->lock before pv->cpustate is read, leading to this: Lock holder Waiter --------------------------------------------------------------- read pv->cpustate (it is PV_CPU_ACTIVE) pv->...

...e previous queue head (in pv_wait_check). + * + * See the comments on those functions to see how the races are being + * addressed. + */ + +/* + * Spin thresholds for queue spinlock + */ +#define QSPIN_THRESHOLD SPIN_THRESHOLD +#define MAYHALT_THRESHOLD 0x10 + +/* + * CPU state flags + */ +#define PV_CPU_ACTIVE 1 /* This CPU is active */ +#define PV_CPU_KICKED 2 /* This CPU is being kicked */ +#define PV_CPU_HALTED -1 /* This CPU is halted */ + +/* + * Special head node pointer value + */ +#define PV_INVALID_HEAD NULL + +/* + * Additional fields to be added to the queue node structure + * + * Th...

...e previous queue head (in pv_wait_check). + * + * See the comments on those functions to see how the races are being + * addressed. + */ + +/* + * Spin thresholds for queue spinlock + */ +#define QSPIN_THRESHOLD SPIN_THRESHOLD +#define MAYHALT_THRESHOLD 0x10 + +/* + * CPU state flags + */ +#define PV_CPU_ACTIVE 1 /* This CPU is active */ +#define PV_CPU_KICKED 2 /* This CPU is being kicked */ +#define PV_CPU_HALTED -1 /* This CPU is halted */ + +/* + * Special head node pointer value + */ +#define PV_INVALID_HEAD NULL + +/* + * Additional fields to be added to the queue node structure + * + * Th...

..._node(struct mcs_spinlock *node) >> +{ >> + struct pv_qnode *pn = (struct pv_qnode *)node; >> + >> + BUILD_BUG_ON(sizeof(struct pv_qnode)> 5*sizeof(struct mcs_spinlock)); >> + >> + if (!pv_enabled()) >> + return; >> + >> + pn->cpustate = PV_CPU_ACTIVE; >> + pn->mayhalt = false; >> + pn->mycpu = smp_processor_id(); >> + pn->head = PV_INVALID_HEAD; >> +} > >> @@ -333,6 +393,7 @@ queue: >> node += idx; >> node->locked = 0; >> node->next = NULL; >> + pv_init_...

..._node(struct mcs_spinlock *node) >> +{ >> + struct pv_qnode *pn = (struct pv_qnode *)node; >> + >> + BUILD_BUG_ON(sizeof(struct pv_qnode)> 5*sizeof(struct mcs_spinlock)); >> + >> + if (!pv_enabled()) >> + return; >> + >> + pn->cpustate = PV_CPU_ACTIVE; >> + pn->mayhalt = false; >> + pn->mycpu = smp_processor_id(); >> + pn->head = PV_INVALID_HEAD; >> +} > >> @@ -333,6 +393,7 @@ queue: >> node += idx; >> node->locked = 0; >> node->next = NULL; >> + pv_init_...

...te: > +static inline void pv_init_node(struct mcs_spinlock *node) > +{ > + struct pv_qnode *pn = (struct pv_qnode *)node; > + > + BUILD_BUG_ON(sizeof(struct pv_qnode) > 5*sizeof(struct mcs_spinlock)); > + > + if (!pv_enabled()) > + return; > + > + pn->cpustate = PV_CPU_ACTIVE; > + pn->mayhalt = false; > + pn->mycpu = smp_processor_id(); > + pn->head = PV_INVALID_HEAD; > +} > @@ -333,6 +393,7 @@ queue: > node += idx; > node->locked = 0; > node->next = NULL; > + pv_init_node(node); > > /* > * We...

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 function pointer instead of a

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 function pointer instead of a

v11->v12: - Based on PeterZ's version of the qspinlock patch (https://lkml.org/lkml/2014/6/15/63). - Incorporated many of the review comments from Konrad Wilk and Paolo Bonzini. - The pvqspinlock code is largely from my previous version with PeterZ's way of going from queue tail to head and his idea of using callee saved calls to KVM and XEN codes. v10->v11: - Use a

v11->v12: - Based on PeterZ's version of the qspinlock patch (https://lkml.org/lkml/2014/6/15/63). - Incorporated many of the review comments from Konrad Wilk and Paolo Bonzini. - The pvqspinlock code is largely from my previous version with PeterZ's way of going from queue tail to head and his idea of using callee saved calls to KVM and XEN codes. v10->v11: - Use a

v5->v6: - Change the optimized 2-task contending code to make it fairer at the expense of a bit of performance. - Add a patch to support unfair queue spinlock for Xen. - Modify the PV qspinlock code to follow what was done in the PV ticketlock. - Add performance data for the unfair lock as well as the PV support code. v4->v5: - Move the optimized 2-task contending code to the

v5->v6: - Change the optimized 2-task contending code to make it fairer at the expense of a bit of performance. - Add a patch to support unfair queue spinlock for Xen. - Modify the PV qspinlock code to follow what was done in the PV ticketlock. - Add performance data for the unfair lock as well as the PV support code. v4->v5: - Move the optimized 2-task contending code to the