Re: Race in kdb()

[Xavier Bru <xavier.bru@xxxxxxxx>]

Ananth N Mavinakayanahalli wrote:

>Hi,
>
>While working on KDB for ppc64, I hit a race in kdb(). Verified that the
>problem exists on x86 too..
>
>Problem occurs when a bp is set on a very frequently hit routine (eg., 
>sys_read() or schedule()), and multiple processors hit the bp 
>simultaneously. This is the problem I am seeing...
>
>        CPU0                            CPU1
>         |                               |
>        kdb(reason = break)              |
>         |                               |
>         |                               |
>        spin_lock()                      |
>         |                               |
>        kdb_initial_cpu = 0;             |
>         |                               |
>        spin_unlock()                    |
>         ..                       kdb(reason = break)
>         |                               |
>         |                      if (reason != KDB_REASON_SWITCH) {
>         |                      if (KDB_IS_RUNNING() && !KDB_STATE(REENTRY))
>         |                              <is true>
>        |                              ....
>         |                               
>         |
>        smp_kdb_stop();
>
>
>Thanks,
>Ananth
>  
>
Hi, Ananth, Keith & all,

Problem also exists on ia64, and becomes more serious when number of 
cpus is important.

-- 

 Sincères salutations.
_____________________________________________________________________
 
Xavier BRU                 BULL ISD/R&D/INTEL office:     FREC B1-422
tel : +33 (0)4 76 29 77 45                    http://www-frec.bull.fr
fax : +33 (0)4 76 29 77 70                 mailto:Xavier.Bru@xxxxxxxx
addr: BULL, 1 rue de Provence, BP 208, 38432 Echirolles Cedex, FRANCE
_____________________________________________________________________


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