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gettimeofday: avoid per-cpu data in calculation

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Because it is difficult to safely update per-cpu data of other cpus in
settimeofday().
This commit is contained in:
NAKAMURA Gou
2015-10-15 15:16:10 +09:00
parent cad72a8562
commit 153a59a6f4
4 changed files with 43 additions and 41 deletions
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46
kernel/syscall.c
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@@ -94,6 +94,9 @@ static char *syscall_name[] MCKERNEL_UNUSED = {
#undef SYSCALL_DELEGATED
};
struct timespec origin_ts;
unsigned long clocks_per_sec;
void check_signal(unsigned long, void *, int);
void do_signal(long rc, void *regs, struct thread *thread, struct sig_pending *pending, int num);
extern unsigned long do_kill(struct thread *thread, int pid, int tid, int sig, struct siginfo *info, int ptracecont);
@@ -4786,30 +4789,26 @@ SYSCALL_DECLARE(get_cpu_id)
return ihk_mc_get_processor_id();
}
void __update_time_from_tsc_delta(unsigned long *tv_sec,
unsigned long *tv_nsec,
unsigned long tsc_delta)
static void calculate_time_from_tsc(struct timespec *ts)
{
unsigned long ns_delta = tsc_delta * ihk_mc_get_ns_per_tsc() / 1000;
unsigned long current_tsc;
time_t sec_delta;
long ns_delta;
*tv_sec += (ns_delta / NS_PER_SEC);
*tv_nsec += (ns_delta % NS_PER_SEC);
if (*tv_nsec > NS_PER_SEC) {
*tv_nsec -= NS_PER_SEC;
++*tv_sec;
current_tsc = rdtsc();
sec_delta = current_tsc / clocks_per_sec;
ns_delta = NS_PER_SEC * (current_tsc % clocks_per_sec)
/ clocks_per_sec;
/* calc. of ns_delta overflows if clocks_per_sec exceeds 18.44 GHz */
ts->tv_sec = origin_ts.tv_sec + sec_delta;
ts->tv_nsec = origin_ts.tv_nsec + ns_delta;
if (ts->tv_nsec >= NS_PER_SEC) {
ts->tv_nsec -= NS_PER_SEC;
++ts->tv_sec;
}
}
void update_cpu_local_time(void)
{
unsigned long tsc = rdtsc();
__update_time_from_tsc_delta(
&cpu_local_var(tv_sec),
&cpu_local_var(tv_nsec),
tsc - cpu_local_var(last_tsc));
cpu_local_var(last_tsc) = tsc;
return;
}
@@ -4820,6 +4819,7 @@ SYSCALL_DECLARE(gettimeofday)
struct timezone *tz = (struct timezone *)ihk_mc_syscall_arg1(ctx);
struct timeval atv;
int error;
struct timespec ats;
if (!tv && !tz) {
/* nothing to do */
@@ -4828,10 +4828,10 @@ SYSCALL_DECLARE(gettimeofday)
/* Do it locally if supported */
if (!tz && gettime_local_support) {
update_cpu_local_time();
calculate_time_from_tsc(&ats);
atv.tv_sec = cpu_local_var(tv_sec);
atv.tv_usec = cpu_local_var(tv_nsec) / 1000;
atv.tv_sec = ats.tv_sec;
atv.tv_usec = ats.tv_nsec / 1000;
error = copy_to_user(tv, &atv, sizeof(atv));