Module Name: xsrc
Committed By: tnn
Date: Sun Feb 23 23:18:01 UTC 2020
Modified Files:
xsrc/external/mit/libxshmfence/dist/src: xshmfence_semaphore.c
xshmfence_semaphore.h
Log Message:
sync from pkgsrc:
> libxshmfence: improve performance of semaphore backend. Bump rev.
>
> It used more locking than necessary. We only need two semaphores.
> One to tell waiters to wake up and one to let the last waiter that
> wakes up notify xshmfence_trigger() it may now return.
To generate a diff of this commit:
cvs rdiff -u -r1.1 -r1.2 \
xsrc/external/mit/libxshmfence/dist/src/xshmfence_semaphore.c \
xsrc/external/mit/libxshmfence/dist/src/xshmfence_semaphore.h
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: xsrc/external/mit/libxshmfence/dist/src/xshmfence_semaphore.c
diff -u xsrc/external/mit/libxshmfence/dist/src/xshmfence_semaphore.c:1.1 xsrc/external/mit/libxshmfence/dist/src/xshmfence_semaphore.c:1.2
--- xsrc/external/mit/libxshmfence/dist/src/xshmfence_semaphore.c:1.1 Sun Aug 14 03:43:37 2016
+++ xsrc/external/mit/libxshmfence/dist/src/xshmfence_semaphore.c Sun Feb 23 23:18:01 2020
@@ -33,12 +33,12 @@
#include "xshmfenceint.h"
-static sem_t *mksemtemp(char *, const char *);
+static sem_t *mksemtemp(char *, size_t, const char *);
-#define LOCK() do {} while (sem_wait(f->lock) != 0)
-#define UNLOCK() do { sem_post(f->lock); } while (0)
-#define COND_WAIT() do {} while (sem_wait(f->cond) != 0)
-#define COND_SIGNAL() do { sem_post(f->cond); } while (0)
+#define COND_WAIT_W() do {} while (sem_wait(f->cond_w) != 0)
+#define COND_SIGNAL_W() do { sem_post(f->cond_w); } while (0)
+#define COND_WAIT_T() do {} while (sem_wait(f->cond_t) != 0)
+#define COND_SIGNAL_T() do { sem_post(f->cond_t); } while (0)
/**
* xshmfence_trigger:
@@ -52,30 +52,23 @@ static sem_t *mksemtemp(char *, const ch
int
xshmfence_trigger(struct xshmfence *f) {
int v, waiting;
- LOCK();
v = __sync_bool_compare_and_swap(&f->triggered, 0, 1);
if (v == 0) {
/* already triggered */
- UNLOCK();
return 0;
}
-
- waiting = __sync_fetch_and_add(&f->waiting, 0);
- while (waiting > 0) {
- COND_SIGNAL();
- waiting--;
- }
-
- while (__sync_fetch_and_add(&f->waiting, 0) > 0) {
- /*
- * Busy wait until they all woke up.
- * No new sleepers should arrive since
- * the lock is still held.
- */
- /* yield(); */
+ while ((waiting = __sync_fetch_and_add(&f->waiting, 0)) > 0) {
+ if (__sync_bool_compare_and_swap(&f->waiting, waiting, 0)) {
+ __sync_fetch_and_add(&f->wakeups, waiting);
+ while (waiting--) {
+ COND_SIGNAL_W();
+ }
+ COND_WAIT_T();
+ return 0;
+ }
}
- UNLOCK();
+
return 0;
}
@@ -92,24 +85,18 @@ xshmfence_trigger(struct xshmfence *f) {
int
xshmfence_await(struct xshmfence *f) {
- LOCK();
if (__sync_fetch_and_add(&f->triggered, 0) == 1) {
- UNLOCK();
return 0;
}
do {
__sync_fetch_and_add(&f->waiting, 1);
- /*
- * These next operations are not atomic.
- * But we busy-wait in xshmfence_trigger, so that's ok.
- */
- UNLOCK();
- COND_WAIT();
- __sync_fetch_and_sub(&f->waiting, 1);
- LOCK();
+ COND_WAIT_W();
+ } while (__sync_fetch_and_add(&f->triggered, 0) == 0);
+
+ if (__sync_sub_and_fetch(&f->wakeups, 1) == 0) {
+ COND_SIGNAL_T();
}
- while (__sync_fetch_and_add(&f->triggered, 0) == 0);
- UNLOCK();
+
return 0;
}
@@ -121,11 +108,7 @@ xshmfence_await(struct xshmfence *f) {
**/
int
xshmfence_query(struct xshmfence *f) {
- int ret;
- LOCK();
- ret = __sync_fetch_and_add(&f->triggered, 0);
- UNLOCK();
- return ret;
+ return __sync_fetch_and_add(&f->triggered, 0);
}
/**
@@ -137,9 +120,7 @@ xshmfence_query(struct xshmfence *f) {
**/
void
xshmfence_reset(struct xshmfence *f) {
- LOCK();
__sync_bool_compare_and_swap(&f->triggered, 1, 0);
- UNLOCK();
}
/**
@@ -151,27 +132,26 @@ xshmfence_reset(struct xshmfence *f) {
void
xshmfence_init(int fd)
{
- sem_t *lock;
- sem_t *cond;
+ sem_t *cond_w, *cond_t;
struct xshmfence f;
__sync_fetch_and_and(&f.refcnt, 0);
__sync_fetch_and_and(&f.triggered, 0);
__sync_fetch_and_and(&f.waiting, 0);
-
- lock = mksemtemp(f.lockname, "/xshmfl-%i");
- if (lock == SEM_FAILED) {
+ __sync_fetch_and_and(&f.wakeups, 0);
+
+ cond_w = mksemtemp(f.condname_w, sizeof(f.condname_w), "w");
+ if (cond_w == SEM_FAILED) {
err(EXIT_FAILURE, "xshmfence_init: sem_open");
}
-
- cond = mksemtemp(f.condname, "/xshmfc-%i");
- if (cond == SEM_FAILED) {
+ cond_t = mksemtemp(f.condname_t, sizeof(f.condname_t), "t");
+ if (cond_t == SEM_FAILED) {
err(EXIT_FAILURE, "xshmfence_init: sem_open");
}
-
- sem_close(lock);
- sem_close(cond);
-
+
+ sem_close(cond_w);
+ sem_close(cond_t);
+
pwrite(fd, &f, sizeof(f), 0);
}
@@ -187,7 +167,7 @@ xshmfence_open_semaphore(struct xshmfenc
/*
* map process local memory to page 2
*/
- if (mmap ((void*)&f->lock,
+ if (mmap ((void*)&f->cond_w,
LIBXSHM_PAGESIZE,
PROT_READ|PROT_WRITE,
MAP_FIXED|MAP_ANON,
@@ -195,11 +175,11 @@ xshmfence_open_semaphore(struct xshmfenc
errx(EXIT_FAILURE, "xshmfence_open_semaphore: mmap failed");
}
- if ((f->lock = sem_open(f->lockname, 0 , 0)) == SEM_FAILED) {
+ if ((f->cond_w = sem_open(f->condname_w, 0)) == SEM_FAILED) {
errx(EXIT_FAILURE, "xshmfence_open_semaphore: sem_open failed");
}
- if ((f->cond = sem_open(f->condname, 0 , 0)) == SEM_FAILED) {
+ if ((f->cond_t = sem_open(f->condname_t, 0)) == SEM_FAILED) {
errx(EXIT_FAILURE, "xshmfence_open_semaphore: sem_open failed");
}
__sync_fetch_and_add(&f->refcnt, 1);
@@ -214,23 +194,24 @@ xshmfence_open_semaphore(struct xshmfenc
void
xshmfence_close_semaphore(struct xshmfence *f)
{
- sem_close(f->lock);
- sem_close(f->cond);
+ sem_close(f->cond_w);
+ sem_close(f->cond_t);
if (__sync_sub_and_fetch(&f->refcnt, 1) == 0) {
- sem_unlink(f->lockname);
- sem_unlink(f->condname);
+ sem_unlink(f->condname_w);
+ sem_unlink(f->condname_t);
}
}
static sem_t *
-mksemtemp(char *name, const char *template)
+mksemtemp(char *name, size_t namelen, const char *suffix)
{
sem_t *ret;
pid_t p;
p = getpid();
for(;;) {
- sprintf(name, template, p);
- ret = sem_open(name, O_CREAT|O_EXCL, 0600, 1);
+ if (snprintf(name, namelen, "/xshmf%s-%d", suffix, p) >= namelen)
+ return SEM_FAILED;
+ ret = sem_open(name, O_CREAT|O_EXCL, 0600, 0);
if (ret == SEM_FAILED) {
if (errno == EEXIST) {
p++;
Index: xsrc/external/mit/libxshmfence/dist/src/xshmfence_semaphore.h
diff -u xsrc/external/mit/libxshmfence/dist/src/xshmfence_semaphore.h:1.1 xsrc/external/mit/libxshmfence/dist/src/xshmfence_semaphore.h:1.2
--- xsrc/external/mit/libxshmfence/dist/src/xshmfence_semaphore.h:1.1 Sun Aug 14 03:43:37 2016
+++ xsrc/external/mit/libxshmfence/dist/src/xshmfence_semaphore.h Sun Feb 23 23:18:01 2020
@@ -43,11 +43,12 @@ struct xshmfence {
int refcnt LOCK_ALIGN;
int triggered LOCK_ALIGN;
int waiting LOCK_ALIGN;
- char lockname[16];
- char condname[16];
+ int wakeups LOCK_ALIGN;
+ char condname_w[16];
+ char condname_t[16];
/* page 2*/
- sem_t *lock PAGE_ALIGN;
- sem_t *cond;
+ sem_t *cond_w PAGE_ALIGN;
+ sem_t *cond_t;
};
void
