CODEWITHSUNDEEP
c++multithreadingpthreads
Steveng
Steveng

Reputation: 1171

pthread sleep linux

I am creating a program with multiple threads using pthreads.

Is sleep() causing the process (all the threads) to stop executing or just the thread where I am calling sleep?

Upvotes: 29

Views: 107550

Answers (6)

rjhcnf
rjhcnf

Reputation: 1057

Posix sleep function is not thread safe. https://clang.llvm.org/extra/clang-tidy/checks/concurrency/mt-unsafe.html

Upvotes: 0

Basile Starynkevitch
Basile Starynkevitch

Reputation: 1

In practice, there are few cases where you just want to sleep for a small delay (milliseconds). For Linux, read time(7), and see also this answer. For a delay of more than a second, see sleep(3), for a small delay, see nanosleep(2). (A counter example might be a RasPerryPi running some embedded Linux and driving a robot; in such case you might indeed read from some hardware device every tenth of seconds). Of course what is sleeping is just a single kernel-scheduled task (so a process or thread).

It is likely that you want to code some event loop. In such a case, you probably want something like poll(2) or select(2), or you want to use condition variables (read a Pthread tutorial about pthread_cond_init etc...) associated with mutexes.

Threads are expensive resources (since each needs a call stack, often of a megabyte at least). You should prefer having one or a few event loops instead of having thousands of threads.

If you are coding for Linux, read also Advanced Linux Programming and syscalls(2) and pthreads(7).

Upvotes: 0

caf
caf

Reputation: 239041

Just the thread. The POSIX documentation for sleep() says:

The sleep() function shall cause the calling thread to be suspended from execution...

Upvotes: 50

Ricky
Ricky

Reputation: 705

sleep() function does not cease a specific thread, but it stops the whole process for the specified amount of time. For stopping the execution of a particular thread, we can use one pthread condition object and use pthread_cond_timedwait() function for making the thread wait for a specific amount of time. Each thread will have its own condition object and it will never receive a signal from any other thread.

Upvotes: -5

Chand Priyankara
Chand Priyankara

Reputation: 6784

Try this,

#include <unistd.h>

usleep(microseconds);

Upvotes: 12

CMorgan
CMorgan

Reputation: 323

I usually use nanosleep and it works fine. Nanosleep supends the execution of the calling thread. I have had the same doubt because in some man pages sleep refers to the entire process.

Upvotes: 6

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