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[glibc] hurd: Fix timeout handling in _hurd_select
- From: Samuel Thibault <sthibaul at sourceware dot org>
- To: glibc-cvs at sourceware dot org
- Date: 29 Aug 2019 23:17:01 -0000
- Subject: [glibc] hurd: Fix timeout handling in _hurd_select
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=c3010778d5846f0f16278f8e94763efb59cd5761
commit c3010778d5846f0f16278f8e94763efb59cd5761
Author: Richard Braun <rbraun@sceen.net>
Date: Fri Aug 30 01:16:37 2019 +0200
hurd: Fix timeout handling in _hurd_select
Rely on servers to implement timeouts, so that very short values (including
0) don't make mach_msg return before valid replies can be received. The
purpose of this scheme is to guarantee a full client-server round-trip,
whatever the timeout value.
This change depends on the new io_select_timeout RPC being implemented by
servers.
* hurd/Makefile (user-interfaces): Add io_reply and io_request.
* hurd/hurdselect.c: Include <sys/time.h>, <hurd/io_request.h> and
<limits.h>.
(_hurd_select): Replace the call to __io_select with either
__io_select_request or __io_select_timeout_request, depending on the
timeout. Count the number of ready descriptors (replies for which at
least one type bit is set). Implement the timeout locally when there is
no file descriptor.
Diff:
---
ChangeLog | 9 ++++-
hurd/Makefile | 3 +-
hurd/hurdselect.c | 116 ++++++++++++++++++++++++++++++++++++------------------
3 files changed, 87 insertions(+), 41 deletions(-)
diff --git a/ChangeLog b/ChangeLog
index d2ec5d5..37cbe28 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,6 +1,5 @@
2019-08-30 Samuel Thibault <samuel.thibault@ens-lyon.org>
-
* sysdeps/mach/hurd/getcwd.c
(_hurd_canonicalize_directory_name_internal): Do not remove the heading
slash if we got an unknown root directory. (__getcwd): Do not fail with
@@ -11,6 +10,14 @@
* hurd/hurdselect.c (_hurd_select): Always call __io_select with no
timeout.
* sysdeps/mach/hurd/setitimer.c (setitimer_locked): Fix preemptor setup.
+ * hurd/Makefile (user-interfaces): Add io_reply and io_request.
+ * hurd/hurdselect.c: Include <sys/time.h>, <hurd/io_request.h> and
+ <limits.h>.
+ (_hurd_select): Replace the call to __io_select with either
+ __io_select_request or __io_select_timeout_request, depending on the
+ timeout. Count the number of ready descriptors (replies for which at
+ least one type bit is set). Implement the timeout locally when there is
+ no file descriptor.
2019-08-29 Mihailo Stojanovic <mihailo.stojanovic@rt-rk.com>
diff --git a/hurd/Makefile b/hurd/Makefile
index 99d33f9..6d9cbf5 100644
--- a/hurd/Makefile
+++ b/hurd/Makefile
@@ -33,7 +33,8 @@ user-interfaces := $(addprefix hurd/,\
process process_request \
msg msg_reply msg_request \
exec exec_startup crash interrupt \
- fs fsys io term tioctl socket ifsock \
+ fs fsys io io_reply io_request \
+ term tioctl socket ifsock \
login password pfinet pci \
)
server-interfaces := hurd/msg faultexc
diff --git a/hurd/hurdselect.c b/hurd/hurdselect.c
index a5e6e26..416e4a3 100644
--- a/hurd/hurdselect.c
+++ b/hurd/hurdselect.c
@@ -16,14 +16,17 @@
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
+#include <sys/time.h>
#include <sys/types.h>
#include <sys/poll.h>
#include <hurd.h>
#include <hurd/fd.h>
+#include <hurd/io_request.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>
#include <stdint.h>
+#include <limits.h>
/* All user select types. */
#define SELECT_ALL (SELECT_READ | SELECT_WRITE | SELECT_URG)
@@ -44,11 +47,13 @@ _hurd_select (int nfds,
{
int i;
mach_port_t portset;
- int got;
+ int got, ready;
error_t err;
fd_set rfds, wfds, xfds;
int firstfd, lastfd;
- mach_msg_timeout_t to = 0;
+ mach_msg_id_t reply_msgid;
+ mach_msg_timeout_t to;
+ struct timespec ts;
struct
{
struct hurd_userlink ulink;
@@ -73,16 +78,39 @@ _hurd_select (int nfds,
return -1;
}
- if (timeout != NULL)
+#define IO_SELECT_REPLY_MSGID (21012 + 100) /* XXX */
+#define IO_SELECT_TIMEOUT_REPLY_MSGID (21031 + 100) /* XXX */
+
+ if (timeout == NULL)
+ reply_msgid = IO_SELECT_REPLY_MSGID;
+ else
{
- if (timeout->tv_sec < 0 || timeout->tv_nsec < 0)
+ struct timeval now;
+
+ if (timeout->tv_sec < 0 || timeout->tv_nsec < 0 ||
+ timeout->tv_nsec >= 1000000000)
{
errno = EINVAL;
return -1;
}
- to = (timeout->tv_sec * 1000
- + (timeout->tv_nsec + 999999) / 1000000);
+ err = __gettimeofday(&now, NULL);
+ if (err)
+ return -1;
+
+ ts.tv_sec = now.tv_sec + timeout->tv_sec;
+ ts.tv_nsec = now.tv_usec * 1000 + timeout->tv_nsec;
+
+ if (ts.tv_nsec >= 1000000000)
+ {
+ ts.tv_sec++;
+ ts.tv_nsec -= 1000000000;
+ }
+
+ if (ts.tv_sec < 0)
+ ts.tv_sec = LONG_MAX; /* XXX */
+
+ reply_msgid = IO_SELECT_TIMEOUT_REPLY_MSGID;
}
if (sigmask && __sigprocmask (SIG_SETMASK, sigmask, &oset))
@@ -236,12 +264,13 @@ _hurd_select (int nfds,
{
int type = d[i].type;
d[i].reply_port = __mach_reply_port ();
- err = __io_select (d[i].io_port, d[i].reply_port, 0, &type);
- switch (err)
+ if (timeout == NULL)
+ err = __io_select_request (d[i].io_port, d[i].reply_port, type);
+ else
+ err = __io_select_timeout_request (d[i].io_port, d[i].reply_port,
+ ts, type);
+ if (!err)
{
- case MACH_RCV_TIMED_OUT:
- /* No immediate response. This is normal. */
- err = 0;
if (firstfd == lastfd)
/* When there's a single descriptor, we don't need a
portset, so just pretend we have one, but really
@@ -262,32 +291,24 @@ _hurd_select (int nfds,
__mach_port_move_member (__mach_task_self (),
d[i].reply_port, portset);
}
- break;
-
- default:
- /* No other error should happen. Callers of select
+ }
+ else
+ {
+ /* No error should happen. Callers of select
don't expect to see errors, so we simulate
readiness of the erring object and the next call
hopefully will get the error again. */
- type = SELECT_ALL;
- /* FALLTHROUGH */
-
- case 0:
- /* We got an answer. */
- if ((type & SELECT_ALL) == 0)
- /* Bogus answer; treat like an error, as a fake positive. */
- type = SELECT_ALL;
-
- /* This port is already ready already. */
- d[i].type &= type;
d[i].type |= SELECT_RETURNED;
++got;
- break;
}
_hurd_port_free (&d[i].cell->port, &d[i].ulink, d[i].io_port);
}
}
+ /* GOT is the number of replies (or errors), while READY is the number of
+ replies with at least one type bit set. */
+ ready = 0;
+
/* Now wait for reply messages. */
if (!err && got == 0)
{
@@ -329,22 +350,35 @@ _hurd_select (int nfds,
} success;
#endif
} msg;
- mach_msg_option_t options = (timeout == NULL ? 0 : MACH_RCV_TIMEOUT);
+ mach_msg_option_t options;
error_t msgerr;
+
+ /* We rely on servers to implement the timeout, but when there are none,
+ do it on the client side. */
+ if (timeout != NULL && firstfd == -1)
+ {
+ options = MACH_RCV_TIMEOUT;
+ to = timeout->tv_sec * 1000 + (timeout->tv_nsec + 999999) / 1000000;
+ }
+ else
+ {
+ options = 0;
+ to = MACH_MSG_TIMEOUT_NONE;
+ }
+
while ((msgerr = __mach_msg (&msg.head,
MACH_RCV_MSG | MACH_RCV_INTERRUPT | options,
0, sizeof msg, portset, to,
MACH_PORT_NULL)) == MACH_MSG_SUCCESS)
{
/* We got a message. Decode it. */
-#define IO_SELECT_REPLY_MSGID (21012 + 100) /* XXX */
#ifdef MACH_MSG_TYPE_BIT
const union typeword inttype =
{ type:
{ MACH_MSG_TYPE_INTEGER_T, sizeof (integer_t) * 8, 1, 1, 0, 0 }
};
#endif
- if (msg.head.msgh_id == IO_SELECT_REPLY_MSGID
+ if (msg.head.msgh_id == reply_msgid
&& msg.head.msgh_size >= sizeof msg.error
&& !(msg.head.msgh_bits & MACH_MSGH_BITS_COMPLEX)
#ifdef MACH_MSG_TYPE_BIT
@@ -362,12 +396,13 @@ _hurd_select (int nfds,
err = EINTR;
goto poll;
}
+ /* Keep in mind msg.success.result can be 0 if a timeout
+ occurred. */
if (msg.error.err
- || msg.head.msgh_size != sizeof msg.success
#ifdef MACH_MSG_TYPE_BIT
|| msg.success.result_type.word != inttype.word
#endif
- || (msg.success.result & SELECT_ALL) == 0)
+ || msg.head.msgh_size != sizeof msg.success)
{
/* Error or bogus reply. Simulate readiness. */
__mach_msg_destroy (&msg.head);
@@ -384,6 +419,9 @@ _hurd_select (int nfds,
&& d[i].reply_port == msg.head.msgh_local_port)
{
d[i].type &= msg.success.result;
+ if (d[i].type)
+ ++ready;
+
d[i].type |= SELECT_RETURNED;
++got;
}
@@ -408,7 +446,7 @@ _hurd_select (int nfds,
/* Interruption on our side (e.g. signal reception). */
err = EINTR;
- if (got)
+ if (ready)
/* At least one descriptor is known to be ready now, so we will
return success. */
err = 0;
@@ -452,9 +490,9 @@ _hurd_select (int nfds,
}
else
{
- /* Below we recalculate GOT to include an increment for each operation
+ /* Below we recalculate READY to include an increment for each operation
allowed on each fd. */
- got = 0;
+ ready = 0;
/* Set the user bitarrays. We only ever have to clear bits, as all
desired ones are initially set. */
@@ -467,15 +505,15 @@ _hurd_select (int nfds,
type = 0;
if (type & SELECT_READ)
- got++;
+ ready++;
else if (readfds)
FD_CLR (i, readfds);
if (type & SELECT_WRITE)
- got++;
+ ready++;
else if (writefds)
FD_CLR (i, writefds);
if (type & SELECT_URG)
- got++;
+ ready++;
else if (exceptfds)
FD_CLR (i, exceptfds);
}
@@ -484,5 +522,5 @@ _hurd_select (int nfds,
if (sigmask && __sigprocmask (SIG_SETMASK, &oset, NULL))
return -1;
- return got;
+ return ready;
}