Re: PR_GetThreadID() fails with SEGV

Jonathan,

Jonathan Leighton wrote:

>> Please provide a crash stack. Even for a deprecated function, I would 
>> not expect a crash. Are you passing a valid PRThread* pointer ?
> 
> Hi Julien -
> 
> I haven't yet tried to create a simple case where this fails, but where 
> I ran into the problem was in NSPR 4.8's socket.c test code.  Line 501 is:
> 
>         DPRINTF(("TCP_Server: Created Serve_Client = 0x%lx\n", t));
> 
> If I replace "t" with "PR_GetThreadID(t)" I get a SEGV on line 1097 of 
> ptthread.c.  I found this to happen in Solaris 5.10 and OpenSolaris 
> 5.11, but not in FreeBSD 7.2, Linux 2.6.28, or Mac OS X 10.5.6 (Intel). 
>  Below is the output from dbx on Solarix 5.10.
> 
> - Jon
> 
> .
> .
> .
> t@2 (l@2) signal SEGV (no mapping at the fault address) in 
> PR_GetThreadID at line 1097 in file "ptthread.c"
>  1097       return (PRUint32)thred->id;  /* and I don't know what they 
> will do with it */
> (dbx) where
> current thread: t@2
> =>[1] PR_GetThreadID(thred = 0xa), line 1097 in "ptthread.c"
>   [2] TCP_Server(arg = 0x8068af0), line 501 in "socket.c"
>   [3] _pt_root(arg = 0x806b408), line 228 in "ptthread.c"
>   [4] _thr_setup(0xfea50200), at 0xfeea7055
>   [5] _lwp_start(0x1, 0xfeb5efac, 0x8052a93, 0xa, 0x0, 0xfea50200), at 
> 0xfeea7340
> (dbx)

Sorry for the late answer.

Your stack clearly shows an invalid PRThread pointer (thred = 0xa) being 
passed to PR_GetThreadID.

I was able to reproduce this crash. Even when not setting the _debug_on 
global variable, and simply fetching the thread id in a local like this, 
in the TCP_Server function :

{
	int tid = PR_GetThreadID(t);
}

It turns out there is some memory corruption in this test program.
The dbx "check -all" feature reports several "read from unallocated" 
from multiple threads. I haven't narrowed down the cause of the 
corruption exactly. Please file a bug on this.