[ceph.git] / ceph / src / seastar / dpdk / examples / performance-thread / pthread_shim / pthread_shim.h

/* SPDX-License-Identifier: BSD-3-Clause
 * Copyright(c) 2015 Intel Corporation
 */

#ifndef _PTHREAD_SHIM_H_
#define _PTHREAD_SHIM_H_

#include <rte_lcore.h>

/*
 * This pthread shim is an example that demonstrates how legacy code
 * that makes use of POSIX pthread services can make use of lthreads
 * with reduced porting effort.
 *
 * N.B. The example is not a complete implementation, only a subset of
 * pthread APIs sufficient to demonstrate the principle of operation
 * are implemented.
 *
 * In general pthread attribute objects do not have equivalent functions
 * in lthreads, and are ignored.
 *
 * There is one exception and that is the use of attr to specify a
 * core affinity in calls to pthread_create.
 *
 * The shim operates as follows:-
 *
 * On initialisation a constructor function uses dlsym to obtain and
 * save the loaded address of the full set of pthread APIs that will
 * be overridden.
 *
 * For each function there is a stub provided that will invoke either
 * the genuine pthread library function saved saved by the constructor,
 * or else the corresponding equivalent lthread function.
 *
 * The stub functions are implemented in pthread_shim.c
 *
 * The stub will take care of adapting parameters, and any police
 * any constraints where lthread functionality differs.
 *
 * The initial thread must always be a pure lthread.
 *
 * The decision whether to invoke the real library function or the lthread
 * function is controlled by a per pthread flag that can be switched
 * on of off by the pthread_override_set() API described below. Typcially
 * this should be done as the first action of the initial lthread.
 *
 * N.B In general it would be poor practice to revert to invoke a real
 * pthread function when running as an lthread, since these may block and
 * effectively stall the lthread scheduler.
 *
 */


/*
 * An exiting lthread must not terminate the pthread it is running in
 * since this would mean terminating the lthread scheduler.
 * We override pthread_exit() with a macro because it is typically declared with
 * __attribute__((noreturn))
 */
void pthread_exit_override(void *v);

#define pthread_exit(v) do { \
	pthread_exit_override((v));	\
	return NULL;	\
} while (0)

/*
 * Enable/Disable pthread override
 * state
 * 0 disable
 * 1 enable
 */
void pthread_override_set(int state);


/*
 * Return pthread override state
 * return
 * 0 disable
 * 1 enable
 */
int pthread_override_get(void);


#endif /* _PTHREAD_SHIM_H_ */
Commit	Line	Data
9f95a23c TL	1	/* SPDX-License-Identifier: BSD-3-Clause
9f95a23c TL	2	* Copyright(c) 2015 Intel Corporation
7c673cae FG	3	*/
	4
	5	#ifndef _PTHREAD_SHIM_H_
	6	#define _PTHREAD_SHIM_H_
11fdf7f2 TL	7
11fdf7f2 TL	8	#include <rte_lcore.h>
7c673cae FG	9
	10	/*
	11	* This pthread shim is an example that demonstrates how legacy code
	12	* that makes use of POSIX pthread services can make use of lthreads
	13	* with reduced porting effort.
	14	*
	15	* N.B. The example is not a complete implementation, only a subset of
	16	* pthread APIs sufficient to demonstrate the principle of operation
	17	* are implemented.
	18	*
	19	* In general pthread attribute objects do not have equivalent functions
	20	* in lthreads, and are ignored.
	21	*
	22	* There is one exception and that is the use of attr to specify a
	23	* core affinity in calls to pthread_create.
	24	*
	25	* The shim operates as follows:-
	26	*
	27	* On initialisation a constructor function uses dlsym to obtain and
	28	* save the loaded address of the full set of pthread APIs that will
	29	* be overridden.
	30	*
	31	* For each function there is a stub provided that will invoke either
	32	* the genuine pthread library function saved saved by the constructor,
	33	* or else the corresponding equivalent lthread function.
	34	*
	35	* The stub functions are implemented in pthread_shim.c
	36	*
	37	* The stub will take care of adapting parameters, and any police
	38	* any constraints where lthread functionality differs.
	39	*
	40	* The initial thread must always be a pure lthread.
	41	*
	42	* The decision whether to invoke the real library function or the lthread
	43	* function is controlled by a per pthread flag that can be switched
	44	* on of off by the pthread_override_set() API described below. Typcially
	45	* this should be done as the first action of the initial lthread.
	46	*
	47	* N.B In general it would be poor practice to revert to invoke a real
	48	* pthread function when running as an lthread, since these may block and
	49	* effectively stall the lthread scheduler.
	50	*
	51	*/
	52
	53
	54	/*
	55	* An exiting lthread must not terminate the pthread it is running in
	56	* since this would mean terminating the lthread scheduler.
	57	* We override pthread_exit() with a macro because it is typically declared with
	58	* __attribute__((noreturn))
	59	*/
	60	void pthread_exit_override(void *v);
	61
	62	#define pthread_exit(v) do { \
	63	pthread_exit_override((v)); \
	64	return NULL; \
	65	} while (0)
	66
	67	/*
	68	* Enable/Disable pthread override
	69	* state
	70	* 0 disable
	71	* 1 enable
	72	*/
73	void pthread_override_set(int state);
74
75
76	/*
77	* Return pthread override state
78	* return
79	* 0 disable
80	* 1 enable
81	*/
82	int pthread_override_get(void);
83
84
85	#endif /* _PTHREAD_SHIM_H_ */