Now that we've removed bd_rdStart from the bpf_d struct, removing
ticks from bpf(4) itself is straightforward.
- bd_rtout becomes a timespec; update bpfioctl() accordingly.
Cap it at MAXTSLP nanoseconds to avoid arithmetic overflow
in bpfread().
- At the start of bpfread(), if a timeout is set, find the end
of the read as an absolute uptime. This is the point where
we want to avoid overflow: if bd_rtout is only MAXTSLP
nanoseconds the timespecadd(3) will effectively never overflow.
- Before going to sleep, if we have a timeout set, compute how
much longer to sleep in nanoseconds.
Here's a spot where an absolute timeout sleep would save a
little code, but we don't have such an interface yet. Worth
keeping in mind for the future, though.
dlg@: You said you wanted to simplify this loop. Unsure what shape
that cleanup would take. Should we clean it up before this change?
Thoughts? ok?
Index: bpf.c
===================================================================
RCS file: /cvs/src/sys/net/bpf.c,v
retrieving revision 1.199
diff -u -p -r1.199 bpf.c
--- bpf.c 26 Dec 2020 16:30:58 -0000 1.199
+++ bpf.c 26 Dec 2020 22:05:04 -0000
@@ -60,6 +60,7 @@
#include <sys/selinfo.h>
#include <sys/sigio.h>
#include <sys/task.h>
+#include <sys/time.h>
#include <net/if.h>
#include <net/bpf.h>
@@ -77,9 +78,6 @@
#define PRINET 26 /* interruptible */
-/* from kern/kern_clock.c; incremented each clock tick. */
-extern int ticks;
-
/*
* The default read buffer size is patchable.
*/
@@ -380,7 +378,7 @@ bpfopen(dev_t dev, int flag, int mode, s
smr_init(&bd->bd_smr);
sigio_init(&bd->bd_sigio);
- bd->bd_rtout = 0; /* no timeout by default */
+ timespecclear(&bd->bd_rtout); /* no timeout by default */
bd->bd_rnonblock = ISSET(flag, FNONBLOCK);
bpf_get(bd);
@@ -428,9 +426,11 @@ bpfclose(dev_t dev, int flag, int mode,
int
bpfread(dev_t dev, struct uio *uio, int ioflag)
{
+ struct timespec diff, end, now;
+ uint64_t nsecs;
struct bpf_d *d;
caddr_t hbuf;
- int end, error, hlen, nticks;
+ int error, hlen, timeout;
KERNEL_ASSERT_LOCKED();
@@ -453,8 +453,11 @@ bpfread(dev_t dev, struct uio *uio, int
/*
* If there's a timeout, mark when the read should end.
*/
- if (d->bd_rtout)
- end = ticks + (int)d->bd_rtout;
+ timeout = timespecisset(&d->bd_rtout);
+ if (timeout) {
+ nanouptime(&now);
+ timespecadd(&now, &d->bd_rtout, &end);
+ }
/*
* If the hold buffer is empty, then do a timed sleep, which
@@ -483,21 +486,26 @@ bpfread(dev_t dev, struct uio *uio, int
if (d->bd_rnonblock) {
/* User requested non-blocking I/O */
error = EWOULDBLOCK;
- } else if (d->bd_rtout == 0) {
+ } else if (timeout == 0) {
/* No read timeout set. */
d->bd_nreaders++;
error = msleep_nsec(d, &d->bd_mtx, PRINET|PCATCH,
"bpf", INFSLP);
d->bd_nreaders--;
- } else if ((nticks = end - ticks) > 0) {
- /* Read timeout has not expired yet. */
- d->bd_nreaders++;
- error = msleep(d, &d->bd_mtx, PRINET|PCATCH, "bpf",
- nticks);
- d->bd_nreaders--;
} else {
- /* Read timeout has expired. */
- error = EWOULDBLOCK;
+ nanouptime(&now);
+ if (timespeccmp(&now, &end, <)) {
+ /* Read timeout has not expired yet. */
+ timespecsub(&end, &now, &diff);
+ nsecs = TIMESPEC_TO_NSEC(&diff);
+ d->bd_nreaders++;
+ error = msleep_nsec(d, &d->bd_mtx,
+ PRINET|PCATCH, "bpf", nsecs);
+ d->bd_nreaders--;
+ } else {
+ /* Read timeout has expired. */
+ error = EWOULDBLOCK;
+ }
}
if (error == EINTR || error == ERESTART)
goto out;
@@ -861,27 +869,17 @@ bpfioctl(dev_t dev, u_long cmd, caddr_t
case BIOCSRTIMEOUT:
{
struct timeval *tv = (struct timeval *)addr;
- u_long rtout;
- /* Compute number of ticks. */
if (tv->tv_sec < 0 || !timerisvalid(tv)) {
error = EINVAL;
break;
}
- if (tv->tv_sec > INT_MAX / hz) {
- error = EOVERFLOW;
- break;
- }
- rtout = tv->tv_sec * hz;
- if (tv->tv_usec / tick > INT_MAX - rtout) {
+ if (TIMEVAL_TO_NSEC(tv) > MAXTSLP) {
error = EOVERFLOW;
break;
}
- rtout += tv->tv_usec / tick;
mtx_enter(&d->bd_mtx);
- d->bd_rtout = rtout;
- if (d->bd_rtout == 0 && tv->tv_usec != 0)
- d->bd_rtout = 1;
+ TIMEVAL_TO_TIMESPEC(tv, &d->bd_rtout);
mtx_leave(&d->bd_mtx);
break;
}
@@ -893,9 +891,9 @@ bpfioctl(dev_t dev, u_long cmd, caddr_t
{
struct timeval *tv = (struct timeval *)addr;
+ memset(tv, 0, sizeof(*tv));
mtx_enter(&d->bd_mtx);
- tv->tv_sec = d->bd_rtout / hz;
- tv->tv_usec = (d->bd_rtout % hz) * tick;
+ TIMESPEC_TO_TIMEVAL(tv, &d->bd_rtout);
mtx_leave(&d->bd_mtx);
break;
}
Index: bpfdesc.h
===================================================================
RCS file: /cvs/src/sys/net/bpfdesc.h,v
retrieving revision 1.43
diff -u -p -r1.43 bpfdesc.h
--- bpfdesc.h 26 Dec 2020 16:30:58 -0000 1.43
+++ bpfdesc.h 26 Dec 2020 22:05:04 -0000
@@ -78,7 +78,7 @@ struct bpf_d {
int bd_in_uiomove; /* for debugging purpose */
struct bpf_if *bd_bif; /* interface descriptor */
- u_long bd_rtout; /* [m] Read timeout in 'ticks' */
+ struct timespec bd_rtout; /* [m] Read timeout if non-zero */
u_long bd_nreaders; /* [m] # threads asleep in bpfread() */
int bd_rnonblock; /* true if nonblocking reads are set */
struct bpf_program_smr
