Skip site navigation (1)Skip section navigation (2) 
Date:      Mon, 24 Aug 2020 12:43:54 +0000 (UTC)
From:      Edward Tomasz Napierala <trasz@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-12@freebsd.org
Subject:   svn commit: r364664 - stable/12/sys/compat/linux
Message-ID:  <202008241243.07OChsIO034334@repo.freebsd.org>
next in thread | raw e-mail | index | archive | help 
Author: trasz
Date: Mon Aug 24 12:43:54 2020
New Revision: 364664
URL: https://svnweb.freebsd.org/changeset/base/364664

Log:
  MFC r358483 by tijl:
  
  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@gmail.com>

Modified:
  stable/12/sys/compat/linux/linux_misc.c
  stable/12/sys/compat/linux/linux_misc.h
Directory Properties:
  stable/12/   (props changed)

Modified: stable/12/sys/compat/linux/linux_misc.c
==============================================================================
--- stable/12/sys/compat/linux/linux_misc.c	Mon Aug 24 12:35:02 2020	(r364663)
+++ stable/12/sys/compat/linux/linux_misc.c	Mon Aug 24 12:43:54 2020	(r364664)
@@ -143,6 +143,11 @@ 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);
 
 
@@ -1586,6 +1591,33 @@ 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);
@@ -1639,6 +1671,20 @@ linux_sched_get_priority_max(struct thread *td,
 		printf(ARGS(sched_get_priority_max, "%d"), args->policy);
 #endif
 
+	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;
@@ -1666,6 +1712,20 @@ linux_sched_get_priority_min(struct thread *td,
 		printf(ARGS(sched_get_priority_min, "%d"), args->policy);
 #endif
 
+	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;
@@ -2123,7 +2183,7 @@ linux_sched_setparam(struct thread *td,
 {
 	struct sched_param sched_param;
 	struct thread *tdt;
-	int error;
+	int error, policy;
 
 #ifdef DEBUG
 	if (ldebug(sched_setparam))
@@ -2138,8 +2198,41 @@ 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);
 }
 
@@ -2149,7 +2242,7 @@ linux_sched_getparam(struct thread *td,
 {
 	struct sched_param sched_param;
 	struct thread *tdt;
-	int error;
+	int error, policy;
 
 #ifdef DEBUG
 	if (ldebug(sched_getparam))
@@ -2161,10 +2254,38 @@ linux_sched_getparam(struct thread *td,
 		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: stable/12/sys/compat/linux/linux_misc.h
==============================================================================
--- stable/12/sys/compat/linux/linux_misc.h	Mon Aug 24 12:35:02 2020	(r364663)
+++ stable/12/sys/compat/linux/linux_misc.h	Mon Aug 24 12:43:54 2020	(r364664)
@@ -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];

Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?202008241243.07OChsIO034334>