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 <iwt...@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]; 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