Reading of timestamps is not atomic in general

[Sebastian Huber]

We use

int64_t

or

struct timespec {

long tv_nsec;
long tv_sec;

};

for timestamps in the Score (Timestamp_Control). The read of such values is in general not atomic. We should provide a function

void _Timestamp_Get( Timestamp_Control *val )

for atomic reads of timestamps. We can use interrupt enable/disable for this, or exploit the monotonic property of timestamps:

do {

s0 = val->tv_sec;
ns0 = val->tv_nsec;
RTEMS_COMPILER_MEMORY_BARRIER();
s1 = val->tv_sec;

} while (s0 != s1);

I prefer the interrupt enable/disable variant.

[Sebastian Huber]

Replying to comment:1:

There is currently no _Timestamp_Get method. Are you proposing to add one that
is atomic?

Yes, we have no _Timestamp_Get() method currently, and we need one.

If so, there will also need to be a _Timestamp_Get_unprotected.

Ok.

[Gedare Bloom]

Replace Version=HEAD with Version=4.11 for the tickets with Milestone >= 4.11

[Sebastian Huber]

In _TOD_Get_with_nanoseconds() interrupts are disabled for the snapshot. No plans to add a general _Timestamp_Get(). The timestamp implementation should be replaced with FreeBSD timecounters.