Sporadic mmap failure

[Shachar Weinstein]

Hi,
My code sporadically crashes in:

#
# Fatal error in ../deps/v8/src/api.h, line 297
# CHECK(allow_empty_handle || that != __null) failed
#

==== Stack trace ============================================

Security context: 0x16fc80a06b71 #0#
    1: map(aka mmap_wrapper) [/root/.znpm_cache/mmap-2.0.1/index.js:18] (this=0x33e128f04119 #1#,size=2844,protection=1,flags=1,fd=15,offset=0x16fc80a04121 )
    2: arguments adaptor frame: 4->5
    3: get_mmap(aka get_mmap) [REDACTED] (this=0x16fc80a04121 ,path=0x2c985e7177f9 ,table=0x2c985e7b5ac9 )

The code loads a few files using the same mmap code with no problem before this point and it does exist (has a valid fd '15').

I've tried looking around for a possible cause for this and found this: nodejs/node-v0.x-archive#5864

I'm not very familiar with wrapped c++ code in node libs, does anyone have an idea of the cause or point me in the right direction?

Thanks,
Shachar W.

[Geo Carncross]

You can post your code if you want.

[Shachar Weinstein]

There's isn't much into my code, this function is the only usage of mmap, it's called about half-dozen times for different files on the module init stage, most of the time all the calls succeed, but once in a while it crashes on one of them (not necessarily the first) with the above callstack.

var mmap = require('mmap');
.....
function get_mmap(path, table)
{
    var file = path+'/'+table, buffer;
    try { buffer = mmap.map(0, mmap.PROT_READ, mmap.MAP_SHARED, file); }
    catch(e) { throw new Error('failed to open '+file+': '+e); }
    zerr.debug('loaded mmap '+file);
    return buffer;
}

[Geo Carncross]

I've published 2.0.2 which does the contortion everyone else seems to be doing. It still works with my tests, but if it doesn't work for you maybe you could make a change to run_test.js that uses global.gc() to trigger the bug?