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libc: dont cache /dev/bintime filedescriptor for nsec()

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This commit is contained in:
cinap_lenrek 2014-05-20 05:01:26 +02:00
parent c7be3ba9e6
commit 7abf926bcf
3 changed files with 9 additions and 92 deletions
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5
sys/man/2/time
View file

@ -28,8 +28,7 @@ is not zero then
is also set to the answer.
.PP
These functions work by reading
.BR /dev/bintime ,
opening that file when they are first called.
.BR /dev/bintime .
.SH SOURCE
.B /sys/src/libc/9sys/time.c
.br
@ -40,5 +39,3 @@ opening that file when they are first called.
.SH DIAGNOSTICS
Sets
.IR errstr .
.SH BUGS
These routines maintain a static file descriptor.

58
sys/src/libc/9sys/nsec.c
View file

@ -1,6 +1,5 @@
#include <u.h>
#include <libc.h>
#include <tos.h>
static uvlong order = 0x0001020304050607ULL;
@ -16,60 +15,19 @@ be2vlong(vlong *to, uchar *f)
t[o[i]] = f[i];
}
static int fd = -1;
static struct {
int pid;
int fd;
} fds[64];
vlong
nsec(void)
{
uchar b[8];
vlong t;
int pid, i, f, tries;
int fd;
/*
* Threaded programs may have multiple procs
* with different fd tables, so we may need to open
* /dev/bintime on a per-pid basis
*/
/* First, look if we've opened it for this particular pid */
pid = _tos->pid;
do{
f = -1;
for(i = 0; i < nelem(fds); i++)
if(fds[i].pid == pid){
f = fds[i].fd;
break;
}
tries = 0;
if(f < 0){
/* If it's not open for this pid, try the global pid */
if(fd >= 0)
f = fd;
else{
/* must open */
if((f = open("/dev/bintime", OREAD|OCEXEC)) < 0)
return 0;
fd = f;
for(i = 0; i < nelem(fds); i++)
if(fds[i].pid == pid || fds[i].pid == 0){
fds[i].pid = pid;
fds[i].fd = f;
break;
}
}
}
if(pread(f, b, sizeof b, 0) == sizeof b){
t = 0;
fd = open("/dev/bintime", OREAD);
if(fd >= 0){
if(pread(fd, b, sizeof b, 0) == sizeof b)
be2vlong(&t, b);
return t;
}
close(f);
if(i < nelem(fds))
fds[i].fd = -1;
}while(tries++ == 0); /* retry once */
USED(tries);
return 0;
close(fd);
}
return t;
}

38
sys/src/libc/9sys/time.c
View file

@ -1,50 +1,12 @@
#include <u.h>
#include <libc.h>
/*
* After a fork with fd's copied, both fd's are pointing to
* the same Chan structure. Since the offset is kept in the Chan
* structure, the seek's and read's in the two processes can
* compete at moving the offset around. Hence the unusual loop
* in the middle of this routine.
*/
static long
oldtime(long *tp)
{
char b[20];
static int f = -1;
int i, retries;
long t;
memset(b, 0, sizeof(b));
for(retries = 0; retries < 100; retries++){
if(f < 0)
f = open("/dev/time", OREAD|OCEXEC);
if(f < 0)
break;
if(seek(f, 0, 0) < 0 || (i = read(f, b, sizeof(b))) < 0){
close(f);
f = -1;
} else {
if(i != 0)
break;
}
}
t = atol(b);
if(tp)
*tp = t;
return t;
}
long
time(long *tp)
{
vlong t;
t = nsec()/1000000000LL;
if(t == 0)
t = oldtime(0);
if(tp != nil)
*tp = t;
return t;