diff options
Diffstat (limited to 'arch/x86/vdso/vclock_gettime.c')
| -rw-r--r-- | arch/x86/vdso/vclock_gettime.c | 48 |
1 files changed, 48 insertions, 0 deletions
diff --git a/arch/x86/vdso/vclock_gettime.c b/arch/x86/vdso/vclock_gettime.c index ee55754cc3c..7bc481508d0 100644 --- a/arch/x86/vdso/vclock_gettime.c +++ b/arch/x86/vdso/vclock_gettime.c @@ -22,6 +22,8 @@ #include <asm/hpet.h> #include <asm/unistd.h> #include <asm/io.h> +#include <asm/trace-clock.h> +#include <asm/timer.h> #include "vextern.h" #define gtod vdso_vsyscall_gtod_data @@ -111,6 +113,46 @@ notrace static noinline int do_monotonic_coarse(struct timespec *ts) return 0; } +/* + * If the TSC is synchronized across all CPUs, read the current TSC + * and export its value in the nsec field of the timespec + */ +notrace static noinline int do_trace_clock(struct timespec *ts) +{ + unsigned long seq; + union lttng_timespec *lts = (union lttng_timespec *) ts; + + do { + seq = read_seqbegin(>od->lock); + if (unlikely(!gtod->trace_clock_is_sync)) + return vdso_fallback_gettime(CLOCK_TRACE, ts); + /* + * We don't protect the rdtsc with the rdtsc_barrier because + * we can't obtain with tracing that level of precision. + * The operation of recording an event is not atomic therefore + * the small chance of imprecision doesn't justify the overhead + * of a barrier. + */ + /* + * TODO: check that vget_cycles(), using paravirt ops, will + * match the TSC read by get_cycles() at the kernel level. + */ + lts->lttng_ts = vget_cycles(); + } while (unlikely(read_seqretry(>od->lock, seq))); + + return 0; +} + +/* + * Returns the cpu_khz, it needs to be a syscall because we can't access + * this value from userspace and it will only be called at the beginning + * of the tracing session + */ +notrace static noinline int do_trace_clock_freq(struct timespec *ts) +{ + return vdso_fallback_gettime(CLOCK_TRACE_FREQ, ts); +} + notrace int __vdso_clock_gettime(clockid_t clock, struct timespec *ts) { if (likely(gtod->sysctl_enabled)) @@ -127,6 +169,12 @@ notrace int __vdso_clock_gettime(clockid_t clock, struct timespec *ts) return do_realtime_coarse(ts); case CLOCK_MONOTONIC_COARSE: return do_monotonic_coarse(ts); + case CLOCK_TRACE: + return do_trace_clock(ts); + case CLOCK_TRACE_FREQ: + return do_trace_clock_freq(ts); + default: + return -EINVAL; } return vdso_fallback_gettime(clock, ts); } |