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kdb,debug_core: adjust master cpu switch logic against new debug_core locking

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The kdb shell needs to enforce switching back to the original CPU that
took the exception before restoring normal kernel execution.  Resuming
from a different CPU than what took the original exception will cause
problems with spin locks that are freed from the a different processor
than had taken the lock.

The special logic in dbg_cpu_switch() can go away entirely with
because the state of what cpus want to be masters or slaves will
remain unchanged between entry and exit of the debug_core exception
context.

Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
This commit is contained in:
Jason Wessel
2010-05-21 08:46:00 -05:00
parent dfee3a7b92
commit 495363d380
3 changed files with 9 additions and 22 deletions
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16
kernel/debug/debug_core.c
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@ -460,19 +460,6 @@ static int kgdb_reenter_check(struct kgdb_state *ks)
return 1;
}
static void dbg_cpu_switch(int cpu, int next_cpu)
{
/* Mark the cpu we are switching away from as a slave when it
* holds the kgdb_active token. This must be done so that the
* that all the cpus wait in for the debug core will not enter
* again as the master. */
if (cpu == atomic_read(&kgdb_active)) {
kgdb_info[cpu].exception_state |= DCPU_IS_SLAVE;
kgdb_info[cpu].exception_state &= ~DCPU_WANT_MASTER;
}
kgdb_info[next_cpu].exception_state |= DCPU_NEXT_MASTER;
}
static void dbg_touch_watchdogs(void)
{
touch_softlockup_watchdog_sync();
@ -638,7 +625,8 @@ cpu_master_loop:
if (error == DBG_PASS_EVENT) {
dbg_kdb_mode = !dbg_kdb_mode;
} else if (error == DBG_SWITCH_CPU_EVENT) {
dbg_cpu_switch(cpu, dbg_switch_cpu);
kgdb_info[dbg_switch_cpu].exception_state |=
DCPU_NEXT_MASTER;
goto cpu_loop;
} else {
kgdb_info[cpu].ret_state = error;