[issue7739] time.strftime may hung while trying to open /etc/localtime but does not release GIL

[Doron Tal]

New submission from Doron Tal <doron.tal.list at gmail.com>:

I've encountered a hung of python process for more than a second. It appears that the stall happens due to time.strftime call, which internally opens a file ('/etc/localtime'). I think it is best if the GIL would have been released to allow other threads to continue working.

Snippet from strace on:
-----------------------
import time
time.strftime('%Z')
-----------------------
Note the line:
open("/etc/localtime", O_RDONLY)        = 4


----=== strace output Starts here  ===---
stat("/usr/local/lib/python2.6/lib-old/time", 0x7fff871deff0) = -1 ENOENT (No such file or directory)
open("/usr/local/lib/python2.6/lib-old/time.so", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/local/lib/python2.6/lib-old/timemodule.so", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/local/lib/python2.6/lib-old/time.py", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/local/lib/python2.6/lib-old/time.pyc", O_RDONLY) = -1 ENOENT (No such file or directory)
stat("/usr/local/lib/python2.6/lib-dynload/time", 0x7fff871deff0) = -1 ENOENT (No such file or directory)
open("/usr/local/lib/python2.6/lib-dynload/time.so", O_RDONLY) = 3
fstat(3, {st_mode=S_IFREG|0755, st_size=46995, ...}) = 0
futex(0x393b4030ec, FUTEX_WAKE_PRIVATE, 2147483647) = 0
open("/usr/local/lib/python2.6/lib-dynload/time.so", O_RDONLY) = 4
read(4, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0000\30\0\0\0\0\0\0"..., 832) = 832
fstat(4, {st_mode=S_IFREG|0755, st_size=46995, ...}) = 0
mmap(NULL, 2115944, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 4, 0) = 0x2adf26fba000
mprotect(0x2adf26fbd000, 2097152, PROT_NONE) = 0
mmap(0x2adf271bd000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 4, 0x3000) = 0x2adf271bd000
close(4)                                = 0
time(NULL)                              = 1263890749
open("/etc/localtime", O_RDONLY)        = 4
fstat(4, {st_mode=S_IFREG|0644, st_size=2197, ...}) = 0
fstat(4, {st_mode=S_IFREG|0644, st_size=2197, ...}) = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x2adf271bf000
read(4, "TZif2\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\4\0\0\0\4\0\0\0\0"..., 4096) = 2197
lseek(4, -1394, SEEK_CUR)               = 803
read(4, "TZif2\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\5\0\0\0\5\0\0\0\0"..., 4096) = 1394
close(4)                                = 0
munmap(0x2adf271bf000, 4096)            = 0
close(3)                                = 0
time(NULL)                              = 1263890749
stat("/etc/localtime", {st_mode=S_IFREG|0644, st_size=2197, ...}) = 0
rt_sigaction(SIGINT, {SIG_DFL, [], SA_RESTORER, 0x393b60e930}, {0x4c4730, [], SA_RESTORER, 0x393b60e930}, 8) = 0
exit_group(0)                           = ?

----------
messages: 98049
nosy: dorontal
severity: normal
status: open
title: time.strftime may hung while trying to open /etc/localtime but does not release GIL
versions: Python 2.6

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue7739>
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