sync.h File Reference

This file provides functions to synchronize Snitch cores. More...

#include <math.h>

Go to the source code of this file.

Functions
volatile uint32_t *	snrt_mutex ()
	Get a pointer to a mutex variable.
void	snrt_mutex_acquire (volatile uint32_t *pmtx)
	Acquire a mutex, blocking.
void	snrt_mutex_ttas_acquire (volatile uint32_t *pmtx)
	Acquire a mutex, blocking.
void	snrt_mutex_release (volatile uint32_t *pmtx)
	Release a previously-acquired mutex.
void	snrt_cluster_hw_barrier ()
	Synchronize cores in a cluster with a hardware barrier, blocking.
void	snrt_inter_cluster_barrier ()
	Synchronize one core from every cluster with the others.
void	snrt_global_barrier ()
	Synchronize all Snitch cores.
void	snrt_partial_barrier (snrt_barrier_t *barr, uint32_t n)
	Generic software barrier.
uint32_t	snrt_global_all_to_all_reduction (uint32_t value)
	Perform a global sum reduction, blocking.
void	snrt_global_reduction_dma (double *dst_buffer, double *src_buffer, size_t len)
	Perform a sum reduction among clusters, blocking.

Detailed Description

This file provides functions to synchronize Snitch cores.

Function Documentation

snrt_cluster_hw_barrier()

void snrt_cluster_hw_barrier ( )

inline

Synchronize cores in a cluster with a hardware barrier, blocking.

Note

Synchronizes all (both DM and compute) cores. All cores must invoke this function, or the calling cores will stall indefinitely.

snrt_global_all_to_all_reduction()

uint32_t snrt_global_all_to_all_reduction ( uint32_t value )

inline

Perform a global sum reduction, blocking.

All cores participate in the reduction and synchronize globally to wait for the reduction to complete. The synchronization is performed via snrt_global_barrier.

Parameters

value

The value to be summed.

Returns

The result of the sum reduction.

Note

Every Snitch core must invoke this function, or the calling cores will stall indefinitely.

snrt_global_barrier()

void snrt_global_barrier ( )

inline

Synchronize all Snitch cores.

Synchronization is performed hierarchically. Within a cluster, cores are synchronized through a hardware barrier (see snrt_cluster_hw_barrier). Clusters are synchronized through a software barrier (see snrt_inter_cluster_barrier).

Note

Every Snitch core must invoke this function, or the calling cores will stall indefinitely.

snrt_global_reduction_dma()

void snrt_global_reduction_dma ( double * dst_buffer, double * src_buffer, size_t len )

inline

Perform a sum reduction among clusters, blocking.

The reduction is performed in a logarithmic fashion. Half of the clusters active in every level of the binary-tree participate as as senders, the other half as receivers. Senders use the DMA to send their data to the respective receiver's destination buffer. The receiver then reduces each element in its destination buffer with the respective element in its source buffer. It then proceeds to the next level in the binary tree.

Parameters

dst_buffer	The pointer to the calling cluster's destination buffer.
src_buffer	The pointer to the calling cluster's source buffer.
len	The amount of data in each buffer.

Note

The destination buffers must lie at the same offset in every cluster's TCDM.

snrt_inter_cluster_barrier()

void snrt_inter_cluster_barrier ( )

inline

Synchronize one core from every cluster with the others.

Implemented as a software barrier.

Note

One core per cluster must invoke this function, or the calling cores will stall indefinitely.

snrt_mutex_acquire()

void snrt_mutex_acquire ( volatile uint32_t * pmtx )

inline

Acquire a mutex, blocking.

Test-and-set (TAS) implementation of a lock.

Parameters

pmtx	A pointer to a variable which can be used as a mutex, i.e. to which all cores have a reference and at a memory location to which atomic accesses can be made. This can be declared e.g. as static volatile uint32_t mtx = 0;.

snrt_mutex_ttas_acquire()

void snrt_mutex_ttas_acquire ( volatile uint32_t * pmtx )

inline

Acquire a mutex, blocking.

Same as snrt_mutex_acquire but acquires the lock using a test and test-and-set (TTAS) strategy.

snrt_partial_barrier()

void snrt_partial_barrier ( snrt_barrier_t * barr, uint32_t n )

inline

Generic software barrier.

Parameters

barr	pointer to a barrier variable.
n	number of harts that have to enter before released.

Note

Exactly the specified number of harts must invoke this function, or the calling cores will stall indefinitely.