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/*
* This file and its contents are supplied under the terms of the
* Common Development and Distribution License ("CDDL"), version 1.0.
* You may only use this file in accordance with the terms of version
* 1.0 of the CDDL.
*
* A full copy of the text of the CDDL should have accompanied this
* source. A copy of the CDDL is also available via the Internet at
* http://www.illumos.org/license/CDDL.
*/
/*
* Copyright 2021 Oxide Computer Company
*/
/*
* This clock backend implements basic support for the following two clocks:
*
* o CLOCK_VIRTUAL This provides the ability to read the amount of
* user CPU time that the calling thread has spent
* on CPU. This is the LMS_USER cpu microstate.
*
* o CLOCK_THREAD_CPUTIME_ID This clock is similar to the above; however, it
* also includes system time. This is the LMS_USER,
* LMS_SYSTEM, and LMS_TRAP microstates combined
* together. We include LMS_TRAP here because that
* is what you see in a thread's lwpstatus file.
*
* At this time, we only provide the ability to read the current time (e.g.
* through a call to clock_gettime(3C)). There is never a case where being able
* to set the time makes sense today and truthfully, lying about a process's
* runtime should be left to mdb -kw. Today, we do not support the ability to
* create interval timers based on this backend (e.g. timer_create(3C) and
* timer_settime(3C)). However, there is no reason that couldn't be added.
*
* A nice simplification here is that this clock is always about reading from
* the current thread. This means that one can always access it. Because the
* calling thread exists and is in this code, it means that we know it is here.
* Any other privilege information is left to the broader kernel.
*
* Because the only difference between these is the question of whether or not
* we include LMS_SYSTEM time in the value, we generally use the same actual
* clock backend functions except for the one that implements
* clk_clock_gettime().
*/
#include <sys/timer.h>
#include <sys/cyclic.h>
#include <sys/msacct.h>
static clock_backend_t clock_thread_usr;
static clock_backend_t clock_thread_usrsys;
static int
clock_thread_settime(timespec_t *ts)
{
return (EINVAL);
}
static int
clock_thread_usr_gettime(timespec_t *ts)
{
hrtime_t hrt;
kthread_t *t = curthread;
klwp_t *lwp = ttolwp(t);
hrt = lwp->lwp_mstate.ms_acct[LMS_USER];
scalehrtime(&hrt);
hrt2ts(hrt, ts);
return (0);
}
static int
clock_thread_usrsys_gettime(timespec_t *ts)
{
hrtime_t hrt;
kthread_t *t = curthread;
/*
* mstate_thread_onproc_time() takes care of doing the following:
*
* o Combining LMS_USER, LMS_SYSTEM, and LMS_TRAP.
* o Ensuring that the result is scaled
* o Ensuring that the time that's elapsed to the point of our asking
* is included. By definition the kernel is executing in LMS_SYSTEM
* so this ensures that we add that time which isn't currently in the
* microstate to this.
*/
thread_lock(t);
hrt = mstate_thread_onproc_time(t);
thread_unlock(t);
hrt2ts(hrt, ts);
return (0);
}
/*
* The question of the resolution here is a thorny one. Technically this would
* really be based upon the resolution of gethrtime_unscaled(), as we can
* actually tell that much due to our use of CPU microstate accounting. However,
* from a timer resolution perspective it's actually quite different and would
* in theory be based on the system tick rate.
*
* This basically leaves us with two options:
*
* 1) Use 'nsec_per_tick' to go down the Hz path.
* 2) Use the cyclic resolution, which basically is kind of the resolution of
* that timer.
*
* POSIX is unclear as to the effect of the resolution in the case of timer_*()
* functions and only really says it is used to impact the implementation of
* clock_settime() which of course isn't actually supported here. As a result,
* we opt to prefer the cyclic resolution, which is closer to the actual
* resolution of this subsystem. Strictly speaking, this might not be completely
* accurate, but should be on current platforms.
*/
static int
clock_thread_getres(timespec_t *ts)
{
hrt2ts(cyclic_getres(), (timestruc_t *)ts);
return (0);
}
static int
clock_thread_timer_create(itimer_t *it, void (*fire)(itimer_t *))
{
return (EINVAL);
}
static int
clock_thread_timer_settime(itimer_t *it, int flags,
const struct itimerspec *when)
{
return (EINVAL);
}
static int
clock_thread_timer_gettime(itimer_t *it, struct itimerspec *when)
{
return (EINVAL);
}
static int
clock_thread_timer_delete(itimer_t *it)
{
return (EINVAL);
}
static void
clock_thread_timer_lwpbind(itimer_t *it)
{
}
void
clock_thread_init(void)
{
/*
* While this clock backends don't support notifications right now, we
* still fill out the default for what it would be.
*/
clock_thread_usr.clk_default.sigev_signo = SIGALRM;
clock_thread_usr.clk_default.sigev_notify = SIGEV_SIGNAL;
clock_thread_usr.clk_default.sigev_value.sival_ptr = NULL;
clock_thread_usr.clk_clock_settime = clock_thread_settime;
clock_thread_usr.clk_clock_gettime = clock_thread_usr_gettime;
clock_thread_usr.clk_clock_getres = clock_thread_getres;
clock_thread_usr.clk_timer_create = clock_thread_timer_create;
clock_thread_usr.clk_timer_settime = clock_thread_timer_settime;
clock_thread_usr.clk_timer_gettime = clock_thread_timer_gettime;
clock_thread_usr.clk_timer_delete = clock_thread_timer_delete;
clock_thread_usr.clk_timer_lwpbind = clock_thread_timer_lwpbind;
clock_thread_usrsys.clk_default.sigev_signo = SIGALRM;
clock_thread_usrsys.clk_default.sigev_notify = SIGEV_SIGNAL;
clock_thread_usrsys.clk_default.sigev_value.sival_ptr = NULL;
clock_thread_usrsys.clk_clock_settime = clock_thread_settime;
clock_thread_usrsys.clk_clock_gettime = clock_thread_usrsys_gettime;
clock_thread_usrsys.clk_clock_getres = clock_thread_getres;
clock_thread_usrsys.clk_timer_create = clock_thread_timer_create;
clock_thread_usrsys.clk_timer_settime = clock_thread_timer_settime;
clock_thread_usrsys.clk_timer_gettime = clock_thread_timer_gettime;
clock_thread_usrsys.clk_timer_delete = clock_thread_timer_delete;
clock_thread_usrsys.clk_timer_lwpbind = clock_thread_timer_lwpbind;
clock_add_backend(CLOCK_VIRTUAL, &clock_thread_usr);
clock_add_backend(CLOCK_THREAD_CPUTIME_ID, &clock_thread_usrsys);
}
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