Mutex not thread safe? PEP-3108.

[Roy Smith]

I'm perusing PEP-3108 and came upon this interesting statement (under the
"Hardly used" section):

mutex [...] Not thread-safe.

How can a mutex, whose sole reason for existence is to mediate thread
safety, not be thread safe?

[skip@pobox.com]

Re: Mutex not thread safe? PEP-3108.

>>>>"Roy" == Roy Smith <roy@panix.comw rites:

RoyI'm perusing PEP-3108 and came upon this interesting statement
Roy(under the "Hardly used" section):

Roymutex [...] Not thread-safe.

RoyHow can a mutex, whose sole reason for existence is to mediate thread
Roysafety, not be thread safe?

Because it is a mutex in name only. Take a look at the code. There is
nothing in there which actually locks the internal data structure against
simultaneous manipulation (a collections.deq ue instance in this case) from
multiple threads.

Skip

[Hrvoje Niksic]

Re: Mutex not thread safe? PEP-3108.

Roy Smith <roy@panix.comw rites:

I'm perusing PEP-3108 and came upon this interesting statement (under the
"Hardly used" section):
>
mutex [...] Not thread-safe.
>
How can a mutex, whose sole reason for existence is to mediate thread
safety, not be thread safe?

"mutex" is a module designed for use with "sched", not for
multithreading:

"""Mutual exclusion -- for use with module sched
[...]
Of course, no multi-threading is implied -- hence the funny interface
for lock, where a function is called once the lock is aquired.
"""

What is called a mutex in multithreading is known in Python as
threading.Lock, and does work with threads.