shm_open fails composing an address path longer than SHM_NAME_MAX

[nferruzzi]

Recently one problem we have been facing on macosx is the impossibility to run steamvr (latest BETA and dk2 0.4.x).

vrserver_osx.txt [...] Fri Sep 05 17:33:54 2014 UTC - VR server (v1408996868) starting up with config=/Applications/Steam.app/Contents/config Fri Sep 05 17:33:54 2014 UTC - Unable to create shared memory for IPC client Fri Sep 05 17:33:54 2014 UTC - Failed to start server with error 302 [...]

After some debugging of vrserver_osx using dtrace I found the problem is caused by shm_open failing with errno ENAMETOOLONG.

[...] 2196/0x1b6ab: 1003347 4 2 read_nocancel(0xF, "[oculus]\r\n\r\n[vortex]\r\n\r\n\r\n\0", 0x1000) = 26 0 2196/0x1b6ab: 1003360 5 3 close_nocancel(0xF) = 0 0 2196/0x1b6ab: 1003370 2 0 shm_open(0x4589C0, 0xA02, 0x1FF) = -1 Err#63 2196/0x1b6ab: 1003379 6 4 write_nocancel(0xE, "Fri Sep 05 11:45:01 2014 UTC - Unable to create shared memory for IPC client\n\0", 0x4D) = 77 0 2196/0x1b6ab: 1003385 4 2 write_nocancel(0xE, "Fri Sep 05 11:45:01 2014 UTC - Failed to start server with error 302\n\0", 0x45) = 69 0 2196/0x1b6ab: 1003396 2 0 shutdown(0xC, 0x1, 0x45) = -1 Err#57 2196/0x1b6ab: 1003403 6 5 close(0xC) = 0 0 [...]

dumping the address of shm_open arg0 I got something like this

"/Shm/VR_nferruzzi_41d166ec_2828"

Basically calls to shm_open should avoid a situation where they are close to this SHM_NAME_MAX limit; unfortunately I can't provide a patch since this repo is not updated :D :(

dtrace scripts used

!/usr/sbin/dtrace -s

syscall::shm_open:entry { printf("addr: 0x%08x -> %s flags: 0x%04x(%s) mode: 0x%04x", arg0, copyinstr(arg0), arg1, (arg1 & O_RDWR) ? "rw" : (arg1 == O_RDONLY) ? "read" : (arg1 & O_CREAT) ? "create" : "other", arg2); }

syscall::shm_open:return { printf("ret: %d errno: %d", arg0, errno); }

[JoeLudwig]

This is great to know. I'll take a look.

[tibbon]

Are there any temporary workarounds currently?