On Wed, May 21, 2025 at 12:14:31PM +0200, Kirill A. Korinsky wrote:
> On Tue, 20 May 2025 23:49:23 +0200,
> Vitaliy Makkoveev <mvs@openbsd.org> wrote:
> > 
> > Since we are here and at least I do hw.cpuspeed measurements, I like to
> > make it mp-safe. Introduce temporary `cpu_cpuspeed_mpsafe' handler
> > pointer and call it lockless if it is set. Kernel lock is pretty enough
> > to call old `cpu_cpuspeed' handler, so we avoid `sysctl_lock'
> > acquisition and useless pages wiring. The rest architectures can be
> > adjusted separately.
> > 
> > ok?
> >
> 
> Make sense and tested on amd64.
> 
> FWIW ok kirill@

Is there a way that does not introduce yet another API?
This feels like one of those changes where cpu_cpuspeed will remain
forever and cpu_cpuspeed_mpsafe will see no additional usage.
 
> > Index: sys/arch/amd64/amd64/identcpu.c
> > ===================================================================
> > RCS file: /cvs/src/sys/arch/amd64/amd64/identcpu.c,v
> > retrieving revision 1.150
> > diff -u -p -r1.150 identcpu.c
> > --- sys/arch/amd64/amd64/identcpu.c	29 Apr 2025 20:19:48 -0000	1.150
> > +++ sys/arch/amd64/amd64/identcpu.c	20 May 2025 21:30:47 -0000
> > @@ -61,9 +61,14 @@ void	tsc_timecounter_init(struct cpu_inf
> >  void	cpu_check_vmm_cap(struct cpu_info *);
> >  #endif /* NVMM > 0 */
> >  
> > +/*
> > + * Locks used to protect data:
> > + *	a	atomic
> > + */
> > +
> >  /* sysctl wants this. */
> >  char cpu_model[48];
> > -int cpuspeed;
> > +int cpuspeed;			/* [a] */
> >  
> >  int amd64_has_xcrypt;
> >  int amd64_pos_cbit;	/* C bit position for SEV */
> > @@ -74,7 +79,7 @@ int has_rdseed;
> >  int
> >  cpu_amd64speed(int *freq)
> >  {
> > -	*freq = cpuspeed;
> > +	*freq = atomic_load_int(&cpuspeed);
> >  	return (0);
> >  }
> >  
> > @@ -620,7 +625,7 @@ identifycpu(struct cpu_info *ci)
> >  
> >  	if (CPU_IS_PRIMARY(ci)) {
> >  		cpuspeed = (freq + 4999) / 1000000;
> > -		cpu_cpuspeed = cpu_amd64speed;
> > +		cpu_cpuspeed_mpsafe = cpu_amd64speed;
> >  	}
> >  
> >  	printf(", %02x-%02x-%02x", ci->ci_family, ci->ci_model,
> > Index: sys/arch/amd64/amd64/k1x-pstate.c
> > ===================================================================
> > RCS file: /cvs/src/sys/arch/amd64/amd64/k1x-pstate.c,v
> > retrieving revision 1.11
> > diff -u -p -r1.11 k1x-pstate.c
> > --- sys/arch/amd64/amd64/k1x-pstate.c	11 Aug 2021 18:31:48 -0000	1.11
> > +++ sys/arch/amd64/amd64/k1x-pstate.c	20 May 2025 21:30:48 -0000
> > @@ -26,6 +26,7 @@
> >  
> >  #include <sys/param.h>
> >  #include <sys/systm.h>
> > +#include <sys/atomic.h>
> >  #include <sys/malloc.h>
> >  #include <sys/sysctl.h>
> >  
> > @@ -106,7 +107,7 @@ k1x_transition(struct k1x_cpu_state *cst
> >  		DELAY(100);
> >  	}
> >  	if (cfid == fid) {
> > -		cpuspeed = cstate->state_table[level].freq;
> > +		atomic_store_int(&cpuspeed, cstate->state_table[level].freq);
> >  #if 0
> >  		(void)printf("Target: %d Current: %d Pstate: %d\n",
> >  		    cstate->state_table[level].freq,
> > Index: sys/arch/amd64/amd64/powernow-k8.c
> > ===================================================================
> > RCS file: /cvs/src/sys/arch/amd64/amd64/powernow-k8.c,v
> > retrieving revision 1.29
> > diff -u -p -r1.29 powernow-k8.c
> > --- sys/arch/amd64/amd64/powernow-k8.c	21 Feb 2022 08:16:08 -0000	1.29
> > +++ sys/arch/amd64/amd64/powernow-k8.c	20 May 2025 21:30:48 -0000
> > @@ -28,6 +28,7 @@
> >  
> >  #include <sys/param.h>
> >  #include <sys/systm.h>
> > +#include <sys/atomic.h>
> >  #include <sys/malloc.h>
> >  #include <sys/sysctl.h>
> >  
> > @@ -271,7 +272,7 @@ k8pnow_transition(struct k8pnow_cpu_stat
> >  	}
> >  
> >  	if (cfid == fid || cvid == vid)
> > -		cpuspeed = cstate->state_table[level].freq;
> > +		atomic_store_int(&cpuspeed, cstate->state_table[level].freq);
> >  }
> >  
> >  /*
> > Index: sys/kern/kern_sysctl.c
> > ===================================================================
> > RCS file: /cvs/src/sys/kern/kern_sysctl.c,v
> > retrieving revision 1.468
> > diff -u -p -r1.468 kern_sysctl.c
> > --- sys/kern/kern_sysctl.c	9 May 2025 14:53:22 -0000	1.468
> > +++ sys/kern/kern_sysctl.c	20 May 2025 21:30:49 -0000
> > @@ -171,6 +171,7 @@ int hw_sysctl_locked(int *, u_int, void 
> >  	struct proc *);
> >  
> >  int (*cpu_cpuspeed)(int *);
> > +int (*cpu_cpuspeed_mpsafe)(int *);
> >  
> >  /*
> >   * Lock to avoid too many processes vslocking a large amount of memory
> > @@ -844,9 +845,24 @@ hw_sysctl(int *name, u_int namelen, void
> >  	case HW_USERMEM:
> >  		return (sysctl_rdint(oldp, oldlenp, newp,
> >  		    ptoa(physmem - uvmexp.wired)));
> > +	case HW_CPUSPEED: {
> > +		int cpuspeed;
> > +
> > +		if (cpu_cpuspeed_mpsafe)
> > +			err = cpu_cpuspeed_mpsafe(&cpuspeed);
> > +		else if (cpu_cpuspeed) {
> > +			KERNEL_LOCK();
> > +			err = cpu_cpuspeed(&cpuspeed);
> > +			KERNEL_UNLOCK();
> > +		} else
> > +			err = EOPNOTSUPP;
> > +
> > +		if (err)
> > +			return (err);
> > +		return (sysctl_rdint(oldp, oldlenp, newp, cpuspeed));
> > +	}
> >  	case HW_DISKNAMES:
> >  	case HW_DISKSTATS:
> > -	case HW_CPUSPEED:
> >  #ifndef	SMALL_KERNEL
> >  	case HW_SENSORS:
> >  	case HW_SETPERF:
> > @@ -911,7 +927,7 @@ int
> >  hw_sysctl_locked(int *name, u_int namelen, void *oldp, size_t *oldlenp,
> >      void *newp, size_t newlen, struct proc *p)
> >  {
> > -	int err, cpuspeed;
> > +	int err;
> >  
> >  	switch (name[0]) {
> >  	case HW_DISKNAMES:
> > @@ -929,13 +945,6 @@ hw_sysctl_locked(int *name, u_int namele
> >  			return err;
> >  		return (sysctl_rdstruct(oldp, oldlenp, newp, diskstats,
> >  		    disk_count * sizeof(struct diskstats)));
> > -	case HW_CPUSPEED:
> > -		if (!cpu_cpuspeed)
> > -			return (EOPNOTSUPP);
> > -		err = cpu_cpuspeed(&cpuspeed);
> > -		if (err)
> > -			return err;
> > -		return (sysctl_rdint(oldp, oldlenp, newp, cpuspeed));
> >  #ifndef SMALL_KERNEL
> >  	case HW_SENSORS:
> >  		return (sysctl_sensors(name + 1, namelen - 1, oldp, oldlenp,
> > Index: sys/sys/sysctl.h
> > ===================================================================
> > RCS file: /cvs/src/sys/sys/sysctl.h,v
> > retrieving revision 1.242
> > diff -u -p -r1.242 sysctl.h
> > --- sys/sys/sysctl.h	29 Apr 2025 02:24:32 -0000	1.242
> > +++ sys/sys/sysctl.h	20 May 2025 21:30:49 -0000
> > @@ -1084,6 +1084,7 @@ int sysctl_sysvipc(int *, u_int, void *,
> >  int sysctl_wdog(int *, u_int, void *, size_t *, void *, size_t);
> >  
> >  extern int (*cpu_cpuspeed)(int *);
> > +extern int (*cpu_cpuspeed_mpsafe)(int *);
> >  extern void (*cpu_setperf)(int);
> >  
> >  int net_ifiq_sysctl(int *, u_int, void *, size_t *, void *, size_t);
> 
> -- 
> wbr, Kirill
> 

-- 
:wq Claudio