Is the gettimeofday function thread safe in Linux?

Question

The current time must be stored globally in order for gettimeofday to work, however I am not sure if the function modifies any global state so that concurrent execution is undefined.

score 23 · Accepted Answer · answered Jul 10 '10 at 17:54

23

gettimeofday is thread safe.

The (posix) functions listed here might not be, gettimeofday is not one of them.

answered Jul 10 '10 at 17:54

nos

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+1 for citation instead of just "it's safe because it shouldn't need to do anything unsafe..." – R.. GitHub STOP HELPING ICE Jul 10 '10 at 18:21

score 3 · Answer 2 · answered Jul 10 '10 at 17:53

3

Yes, it is thread-safe. The only data it modifies is in the structures you pass pointers to, so an implementation that wasn't thread-safe would have to be doing something spooky.

Best of luck on your project.

answered Jul 10 '10 at 17:53

Ratzkewatzke

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score 2 · Answer 3 · answered Jul 10 '10 at 17:59

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In glibc the gettimeofday(2) is a simple wrapper around a system call (it's a vsyscall actually). No data is touched in the userland. It is thread-safe.

answered Jul 10 '10 at 17:59

Nikolai Fetissov

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score 1 · Answer 4 · answered Jul 10 '10 at 18:02

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No data is modified with this call. You just get a copy. Hence its completely thread safe.

answered Jul 10 '10 at 18:02

Praveen S

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Is the gettimeofday function thread safe in Linux?

4 Answers4

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