svn commit: r358483 - head/sys/compat/linux
Tijl Coosemans
tijl at FreeBSD.org
Sun Mar 1 13:12:05 UTC 2020
Author: tijl
Date: Sun Mar 1 13:12:04 2020
New Revision: 358483
URL: https://svnweb.freebsd.org/changeset/base/358483
Log:
linuxulator: Map scheduler priorities to Linux priorities.
On Linux the valid range of priorities for the SCHED_FIFO and SCHED_RR
scheduling policies is [1,99]. For SCHED_OTHER the single valid priority is
0. On FreeBSD it is [0,31] for all policies. Programs are supposed to
query the valid range using sched_get_priority_(min|max), but of course some
programs assume the Linux values are valid.
This commit adds a tunable compat.linux.map_sched_prio. When enabled
sched_get_priority_(min|max) return the Linux values and sched_setscheduler
and sched_(get|set)param translate between FreeBSD and Linux values.
Because there are more Linux levels than FreeBSD levels, multiple Linux
levels map to a single FreeBSD level, which means pre-emption might not
happen as it does on Linux, so the tunable allows to disable this behaviour.
It is enabled by default because I think it is unlikely that anyone runs
real-time software under Linux emulation on FreeBSD that critically relies
on correct pre-emption.
This fixes FMOD, a commercial sound library used by several games.
PR: 240043
Tested by: Alex S <iwtcex at gmail.com>
Reviewed by: dchagin
MFC after: 2 weeks
Differential Revision: https://reviews.freebsd.org/D23790
Modified:
head/sys/compat/linux/linux_misc.c
head/sys/compat/linux/linux_misc.h
Modified: head/sys/compat/linux/linux_misc.c
==============================================================================
--- head/sys/compat/linux/linux_misc.c Sun Mar 1 12:34:27 2020 (r358482)
+++ head/sys/compat/linux/linux_misc.c Sun Mar 1 13:12:04 2020 (r358483)
@@ -144,6 +144,11 @@ struct l_pselect6arg {
l_size_t ss_len;
};
+static bool map_sched_prio = true;
+SYSCTL_BOOL(_compat_linux, OID_AUTO, map_sched_prio, CTLFLAG_RDTUN,
+ &map_sched_prio, 0, "Map scheduler priorities to Linux priorities "
+ "(not POSIX compliant)");
+
static int linux_utimensat_nsec_valid(l_long);
@@ -1419,6 +1424,33 @@ linux_sched_setscheduler(struct thread *td,
if (error)
return (error);
+ if (map_sched_prio) {
+ switch (policy) {
+ case SCHED_OTHER:
+ if (sched_param.sched_priority != 0)
+ return (EINVAL);
+
+ sched_param.sched_priority =
+ PRI_MAX_TIMESHARE - PRI_MIN_TIMESHARE;
+ break;
+ case SCHED_FIFO:
+ case SCHED_RR:
+ if (sched_param.sched_priority < 1 ||
+ sched_param.sched_priority >= LINUX_MAX_RT_PRIO)
+ return (EINVAL);
+
+ /*
+ * Map [1, LINUX_MAX_RT_PRIO - 1] to
+ * [0, RTP_PRIO_MAX - RTP_PRIO_MIN] (rounding down).
+ */
+ sched_param.sched_priority =
+ (sched_param.sched_priority - 1) *
+ (RTP_PRIO_MAX - RTP_PRIO_MIN + 1) /
+ (LINUX_MAX_RT_PRIO - 1);
+ break;
+ }
+ }
+
tdt = linux_tdfind(td, args->pid, -1);
if (tdt == NULL)
return (ESRCH);
@@ -1462,6 +1494,20 @@ linux_sched_get_priority_max(struct thread *td,
{
struct sched_get_priority_max_args bsd;
+ if (map_sched_prio) {
+ switch (args->policy) {
+ case LINUX_SCHED_OTHER:
+ td->td_retval[0] = 0;
+ return (0);
+ case LINUX_SCHED_FIFO:
+ case LINUX_SCHED_RR:
+ td->td_retval[0] = LINUX_MAX_RT_PRIO - 1;
+ return (0);
+ default:
+ return (EINVAL);
+ }
+ }
+
switch (args->policy) {
case LINUX_SCHED_OTHER:
bsd.policy = SCHED_OTHER;
@@ -1484,6 +1530,20 @@ linux_sched_get_priority_min(struct thread *td,
{
struct sched_get_priority_min_args bsd;
+ if (map_sched_prio) {
+ switch (args->policy) {
+ case LINUX_SCHED_OTHER:
+ td->td_retval[0] = 0;
+ return (0);
+ case LINUX_SCHED_FIFO:
+ case LINUX_SCHED_RR:
+ td->td_retval[0] = 1;
+ return (0);
+ default:
+ return (EINVAL);
+ }
+ }
+
switch (args->policy) {
case LINUX_SCHED_OTHER:
bsd.policy = SCHED_OTHER;
@@ -1864,7 +1924,7 @@ linux_sched_setparam(struct thread *td,
{
struct sched_param sched_param;
struct thread *tdt;
- int error;
+ int error, policy;
error = copyin(uap->param, &sched_param, sizeof(sched_param));
if (error)
@@ -1874,8 +1934,41 @@ linux_sched_setparam(struct thread *td,
if (tdt == NULL)
return (ESRCH);
+ if( map_sched_prio ) {
+ error = kern_sched_getscheduler(td, tdt, &policy);
+ if (error)
+ goto out;
+
+ switch (policy) {
+ case SCHED_OTHER:
+ if (sched_param.sched_priority != 0) {
+ error = EINVAL;
+ goto out;
+ }
+ sched_param.sched_priority =
+ PRI_MAX_TIMESHARE - PRI_MIN_TIMESHARE;
+ break;
+ case SCHED_FIFO:
+ case SCHED_RR:
+ if (sched_param.sched_priority < 1 ||
+ sched_param.sched_priority >= LINUX_MAX_RT_PRIO) {
+ error = EINVAL;
+ goto out;
+ }
+ /*
+ * Map [1, LINUX_MAX_RT_PRIO - 1] to
+ * [0, RTP_PRIO_MAX - RTP_PRIO_MIN] (rounding down).
+ */
+ sched_param.sched_priority =
+ (sched_param.sched_priority - 1) *
+ (RTP_PRIO_MAX - RTP_PRIO_MIN + 1) /
+ (LINUX_MAX_RT_PRIO - 1);
+ break;
+ }
+ }
+
error = kern_sched_setparam(td, tdt, &sched_param);
- PROC_UNLOCK(tdt->td_proc);
+out: PROC_UNLOCK(tdt->td_proc);
return (error);
}
@@ -1885,17 +1978,45 @@ linux_sched_getparam(struct thread *td,
{
struct sched_param sched_param;
struct thread *tdt;
- int error;
+ int error, policy;
tdt = linux_tdfind(td, uap->pid, -1);
if (tdt == NULL)
return (ESRCH);
error = kern_sched_getparam(td, tdt, &sched_param);
- PROC_UNLOCK(tdt->td_proc);
- if (error == 0)
- error = copyout(&sched_param, uap->param,
- sizeof(sched_param));
+ if (error) {
+ PROC_UNLOCK(tdt->td_proc);
+ return (error);
+ }
+
+ if (map_sched_prio) {
+ error = kern_sched_getscheduler(td, tdt, &policy);
+ PROC_UNLOCK(tdt->td_proc);
+ if (error)
+ return (error);
+
+ switch (policy) {
+ case SCHED_OTHER:
+ sched_param.sched_priority = 0;
+ break;
+ case SCHED_FIFO:
+ case SCHED_RR:
+ /*
+ * Map [0, RTP_PRIO_MAX - RTP_PRIO_MIN] to
+ * [1, LINUX_MAX_RT_PRIO - 1] (rounding up).
+ */
+ sched_param.sched_priority =
+ (sched_param.sched_priority *
+ (LINUX_MAX_RT_PRIO - 1) +
+ (RTP_PRIO_MAX - RTP_PRIO_MIN - 1)) /
+ (RTP_PRIO_MAX - RTP_PRIO_MIN) + 1;
+ break;
+ }
+ } else
+ PROC_UNLOCK(tdt->td_proc);
+
+ error = copyout(&sched_param, uap->param, sizeof(sched_param));
return (error);
}
Modified: head/sys/compat/linux/linux_misc.h
==============================================================================
--- head/sys/compat/linux/linux_misc.h Sun Mar 1 12:34:27 2020 (r358482)
+++ head/sys/compat/linux/linux_misc.h Sun Mar 1 13:12:04 2020 (r358483)
@@ -105,6 +105,8 @@ extern const char *linux_kplatform;
#define LINUX_SCHED_FIFO 1
#define LINUX_SCHED_RR 2
+#define LINUX_MAX_RT_PRIO 100
+
struct l_new_utsname {
char sysname[LINUX_MAX_UTSNAME];
char nodename[LINUX_MAX_UTSNAME];
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