Why does IPC::SysV->shmget respond with EINVAL?

Question

I am currently running perl 5.8.8 on a server and I'm trying to install 5.14.

I configured it to usethreads and use64bitint and otherwise the defaults it suggested.

make ran without problems, but make test is failing, on

../cpan/IPC-SysV/t/ipcsysv.t
../cpan/IPC-SysV/t/shm.t

thus:

# ./perl harness ../cpan/IPC-SysV/t/shm.t ../cpan/IPC-SysV/t/ipcsysv.t 
../cpan/IPC-SysV/t/shm.t ...... IPC::SharedMem->new failed: Invalid argument at t/shm.t line 54.
../cpan/IPC-SysV/t/shm.t ...... Dubious, test returned 22 (wstat 5632, 0x1600)
No subtests run
../cpan/IPC-SysV/t/ipcsysv.t .. 1/38 shmget failed: Invalid argument at t/ipcsysv.t line 100.
# Looks like you planned 38 tests but ran 17.
# Looks like your test exited with 22 just after 17.
../cpan/IPC-SysV/t/ipcsysv.t .. Dubious, test returned 22 (wstat 5632, 0x1600)
Failed 21/38 subtests

Test Summary Report
-------------------
../cpan/IPC-SysV/t/shm.t    (Wstat: 5632 Tests: 0 Failed: 0)
  Non-zero exit status: 22
  Parse errors: No plan found in TAP output
../cpan/IPC-SysV/t/ipcsysv.t (Wstat: 5632 Tests: 17 Failed: 0)
  Non-zero exit status: 22
  Parse errors: Bad plan.  You planned 38 tests but ran 17.
Files=2, Tests=17,  0 wallclock secs ( 0.01 usr  0.00 sys +  0.13 cusr  0.00 csys =  0.14 CPU)
Result: FAIL

Both of these tests are reporting 'Invalid argument', but when I look at the source, I can't see anything that looks invalid. I'm not really sure how to proceed... any pointers?

UPDATE

I ran

 strace perl -MIPC::SysV=IPC_PRIVATE,S_IRWXU -e 'shmget(IPC_PRIVATE, 8, S_IRWXU) or die $!'

on two servers: one which is having these problems and one which is not.

There was a lot of output, but what appears interesting is this:

GOOD:

.
.
.
stat64("/usr/lib/perl5/site_perl/5.8.8/i386-linux-thread-multi/auto/IPC/SysV", 0x9d7f0c8) = -1 ENOENT (No such file or directory)
stat64("/usr/lib/perl5/site_perl/5.8.8/auto/IPC/SysV", 0x9d7f0c8) = -1 ENOENT (No such file or directory)
stat64("/usr/lib/perl5/site_perl/auto/IPC/SysV", 0x9d7f0c8) = -1 ENOENT (No such file or directory)
stat64("/usr/lib/perl5/vendor_perl/5.8.8/i386-linux-thread-multi/auto/IPC/SysV", 0x9d7f0c8) = -1 ENOENT (No such file or directory)
stat64("/usr/lib/perl5/vendor_perl/5.8.8/auto/IPC/SysV", 0x9d7f0c8) = -1 ENOENT (No such file or directory)
stat64("/usr/lib/perl5/vendor_perl/auto/IPC/SysV", 0x9d7f0c8) = -1 ENOENT (No such file or directory)
stat64("/usr/lib/perl5/5.8.8/i386-linux-thread-multi/auto/IPC/SysV", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
stat64("/usr/lib/perl5/5.8.8/i386-linux-thread-multi/auto/IPC/SysV/SysV.so", {st_mode=S_IFREG|0755, st_size=15072, ...}) = 0
stat64("/usr/lib/perl5/5.8.8/i386-linux-thread-multi/auto/IPC/SysV/SysV.bs", 0x9d7f0c8) = -1 ENOENT (No such file or directory)
futex(0x4d106c, FUTEX_WAKE_PRIVATE, 2147483647) = 0
open("/usr/lib/perl5/5.8.8/i386-linux-thread-multi/auto/IPC/SysV/SysV.so", O_RDONLY) = 4
read(4, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0\3\0\1\0\0\0 \v\0\0004\0\0\0"..., 512) = 512
fstat64(4, {st_mode=S_IFREG|0755, st_size=15072, ...}) = 0
mmap2(NULL, 17948, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 4, 0) = 0x588000
mmap2(0x58c000, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 4, 0x3) = 0x58c000
close(4)                                = 0
close(3)                                = 0
shmget(IPC_PRIVATE, 8, 0700)            = 7438344
exit_group(0)                      

BAD:

.
.
.
stat64("/usr/lib/perl5/site_perl/5.8.8/i386-linux-thread-multi/auto/IPC/SysV", 0x8d290c8) = -1 ENOENT (No such file or directory)
stat64("/usr/lib/perl5/site_perl/5.8.8/auto/IPC/SysV", 0x8d290c8) = -1 ENOENT (No such file or directory)
stat64("/usr/lib/perl5/site_perl/auto/IPC/SysV", 0x8d290c8) = -1 ENOENT (No such file or directory)
stat64("/usr/lib/perl5/vendor_perl/5.8.8/i386-linux-thread-multi/auto/IPC/SysV", 0x8d290c8) = -1 ENOENT (No such file or directory)
stat64("/usr/lib/perl5/vendor_perl/5.8.8/auto/IPC/SysV", 0x8d290c8) = -1 ENOENT (No such file or directory)
stat64("/usr/lib/perl5/vendor_perl/auto/IPC/SysV", 0x8d290c8) = -1 ENOENT (No such file or directory)
stat64("/usr/lib/perl5/5.8.8/i386-linux-thread-multi/auto/IPC/SysV", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
stat64("/usr/lib/perl5/5.8.8/i386-linux-thread-multi/auto/IPC/SysV/SysV.so", {st_mode=S_IFREG|0755, st_size=15072, ...}) = 0
stat64("/usr/lib/perl5/5.8.8/i386-linux-thread-multi/auto/IPC/SysV/SysV.bs", 0x8d290c8) = -1 ENOENT (No such file or directory)
futex(0x94306c, FUTEX_WAKE_PRIVATE, 2147483647) = 0
open("/usr/lib/perl5/5.8.8/i386-linux-thread-multi/auto/IPC/SysV/SysV.so", O_RDONLY) = 4
read(4, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0\3\0\1\0\0\0 \v\0\0004\0\0\0"..., 512) = 512
fstat64(4, {st_mode=S_IFREG|0755, st_size=15072, ...}) = 0
mmap2(NULL, 17948, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 4, 0) = 0x6a4000
mmap2(0x6a8000, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 4, 0x3) = 0x6a8000
close(4)                                = 0
close(3)                                = 0
shmget(IPC_PRIVATE, 8, 0700)            = -1 EINVAL (Invalid argument)
open("/usr/share/locale/locale.alias", O_RDONLY) = 3
fstat64(3, {st_mode=S_IFREG|0644, st_size=2528, ...}) = 0
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7dbe000
read(3, "# Locale name alias data base.\n#"..., 4096) = 2528
read(3, "", 4096)                       = 0
close(3)                                = 0
munmap(0xb7dbe000, 4096)                = 0
open("/usr/share/locale/en_US.UTF-8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/share/locale/en_US.utf8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/share/locale/en_US/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/share/locale/en.UTF-8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/share/locale/en.utf8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/share/locale/en/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
write(2, "Invalid argument at -e line 1.\n", 31Invalid argument at -e line 1.
) = 31
exit_group(22)                          = ?

So, it appears that the same thing is happening on both servers, it's just that on one, I see shmget(IPC_PRIVATE, 8, 0700) = 7438344

and the other, I see

shmget(IPC_PRIVATE, 8, 0700)            = -1 EINVAL (Invalid argument)

The versions of IPC::SysV are the same on both servers... but it looks to me that this isn't relevant, and that the problem is the the code making the system call... right?

What next?

** UPDATE 2 **

After some googling, I ran the following:

GOOD:

#  cat /proc/sys/kernel/shmmax
4294967295

BAD:

# cat /proc/sys/kernel/shmmax
0

So, that explains the EINVAL, since (from the man pages)

EINVAL

A new segment was to be created and size < SHMMIN or size > SHMMAX, or no new segment was to be created, a segment with given key existed, but size is greater than the size of that segment.

Now, my question is, is there a good reason why this might be set at zero?

Answer 1

Problem solved.

The /etc/sysctl.conf file contained the following:

kernel.shmmax = 137438953472

This is a 64 bit value, but the system is a 32 bit system.

As a result, the SHMMAX value was being set to 0, making all calls to shmget fail.

Changing it to

kernel.shmmax = 4294967295

And using

echo 4294967295 >/proc/sys/kernel/shmmax

I changed the value of SHMMAX and the test completed successfully.