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coretemp(4): Switch to smp_rendezvous_cpus().

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Use of smp_rendezvous_cpus() instead of sched_bind() allows to not
block indefinitely if target CPU is running some thread with higher
priority, while all we need is single rdmsr/wrmsr instruction call.
I guess it should also be much cheaper than full thread migration.

MFC after:	2 weeks
Sponsored by:	iXsystems, Inc.
This commit is contained in:
Alexander Motin 2021-07-29 23:16:22 -04:00
parent 6f179693c5
commit 74f80bc1af
1 changed files with 36 additions and 21 deletions
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57
sys/dev/coretemp/coretemp.c
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@ -42,7 +42,7 @@ __FBSDID("$FreeBSD$");
#include <sys/module.h>
#include <sys/mutex.h>
#include <sys/proc.h> /* for curthread */
#include <sys/sched.h>
#include <sys/smp.h>
#include <sys/sysctl.h>
#include <sys/systm.h>
@ -310,14 +310,32 @@ coretemp_detach(device_t dev)
return (0);
}
struct coretemp_args {
u_int msr;
uint64_t val;
};
static void
coretemp_rdmsr(void *arg)
{
struct coretemp_args *args = arg;
args->val = rdmsr(args->msr);
}
static void
coretemp_wrmsr(void *arg)
{
struct coretemp_args *args = arg;
wrmsr(args->msr, args->val);
}
static uint64_t
coretemp_get_thermal_msr(int cpu)
{
uint64_t msr;
thread_lock(curthread);
sched_bind(curthread, cpu);
thread_unlock(curthread);
struct coretemp_args args;
cpuset_t cpus;
/*
* The digital temperature reading is located at bit 16
@ -329,27 +347,24 @@ coretemp_get_thermal_msr(int cpu)
* The temperature is computed by subtracting the temperature
* reading by Tj(max).
*/
msr = rdmsr(MSR_THERM_STATUS);
thread_lock(curthread);
sched_unbind(curthread);
thread_unlock(curthread);
return (msr);
args.msr = MSR_THERM_STATUS;
CPU_SETOF(cpu, &cpus);
smp_rendezvous_cpus(cpus, smp_no_rendezvous_barrier, coretemp_rdmsr,
smp_no_rendezvous_barrier, &args);
return (args.val);
}
static void
coretemp_clear_thermal_msr(int cpu)
{
thread_lock(curthread);
sched_bind(curthread, cpu);
thread_unlock(curthread);
struct coretemp_args args;
cpuset_t cpus;
wrmsr(MSR_THERM_STATUS, 0);
thread_lock(curthread);
sched_unbind(curthread);
thread_unlock(curthread);
args.msr = MSR_THERM_STATUS;
args.val = 0;
CPU_SETOF(cpu, &cpus);
smp_rendezvous_cpus(cpus, smp_no_rendezvous_barrier, coretemp_wrmsr,
smp_no_rendezvous_barrier, &args);
}
static int