Re: help with pthread_t deprecation / api changes

[Stephen Hemminger <stephen@networkplumber.org>]

On Fri, 09 Dec 2022 22:14:33 +0100
Thomas Monjalon <thomas@monjalon.net> wrote:

> 09/12/2022 17:48, Stephen Hemminger:
> > On Fri, 09 Dec 2022 08:53:57 +0100
> > Thomas Monjalon <thomas@monjalon.net> wrote:
> >   
> > > > > If some execution environment doesn't support thread names, it could return a string that makes it possible for a human to identify the thread, e.g. the tread id. Again, this is assuming that it is only used for debugging, trace, and similar.    
> > > > 
> > > > i think this raises a good question. is the purpose of setting a thread name
> > > > meant to be something we can use from the application or is it something that
> > > > is for debugging diagnostics and may be a best effort?    
> > > 
> > > I think yes it is only for debugging.
> > > So best effort looks to be a good approach.
> > > I'm not sure you need to replace the functions.
> > > Can you just complete the implementations?  
> > 
> > 
> > Surprisingly, thread names are not preserved in core dumps.
> > The core dump standard used by Linux does not put thread name in the image.
> > Since this is a ELF ABI unlikely to be ever be added.  
> 
> What is missing exactly to have thread name in the core dump?
> 
> 

Linux core dump file format is ELF.
The thread info is storewd in the file notes as NT_PRPSINFO
which contains info but not the thread name. In the kernel
thread name is under comm.


typedef struct prpsinfo {       /* Information about process                 */
  unsigned char  pr_state;      /* Numeric process state                     */
  char           pr_sname;      /* Char for pr_state                         */
  unsigned char  pr_zomb;       /* Zombie                                    */
  signed char    pr_nice;       /* Nice val                                  */
  unsigned long  pr_flag;       /* Flags                                     */

  uint32_t       pr_uid;        /* User ID                                   */
  uint32_t       pr_gid;        /* Group ID                                  */

  pid_t          pr_pid;        /* Process ID                                */
  pid_t          pr_ppid;       /* Parent's process ID                       */
  pid_t          pr_pgrp;       /* Group ID                                  */
  pid_t          pr_sid;        /* Session ID                                */
  char           pr_fname[16];  /* Filename of executable                    */
  char           pr_psargs[80]; /* Initial part of arg list                  */
} prpsinfo;


Stack Overflow leads to this pages
https://www.gabriel.urdhr.fr/2015/05/29/core-file/
https://uhlo.blogspot.com/2012/05/brief-look-into-core-dumps.html

Only know this because of investigating how to get thread names
to show up in Azure with Watson.