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

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
View File

@ -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;

3
kernel/debug/kdb/kdb_debugger.c
View File

@ -86,7 +86,7 @@ int kdb_stub(struct kgdb_state *ks)
}
/* Set initial kdb state variables */
KDB_STATE_CLEAR(KGDB_TRANS);
kdb_initial_cpu = ks->cpu;
kdb_initial_cpu = atomic_read(&kgdb_active);
kdb_current_task = kgdb_info[ks->cpu].task;
kdb_current_regs = kgdb_info[ks->cpu].debuggerinfo;
/* Remove any breakpoints as needed by kdb and clear single step */
@ -105,7 +105,6 @@ int kdb_stub(struct kgdb_state *ks)
ks->pass_exception = 1;
KDB_FLAG_SET(CATASTROPHIC);
}
kdb_initial_cpu = ks->cpu;
if (KDB_STATE(SSBPT) && reason == KDB_REASON_SSTEP) {
KDB_STATE_CLEAR(SSBPT);
KDB_STATE_CLEAR(DOING_SS);

12
kernel/debug/kdb/kdb_main.c
View File

@ -1749,13 +1749,13 @@ static int kdb_go(int argc, const char **argv)
int nextarg;
long offset;
if (raw_smp_processor_id() != kdb_initial_cpu) {
kdb_printf("go must execute on the entry cpu, "
"please use \"cpu %d\" and then execute go\n",
kdb_initial_cpu);
return KDB_BADCPUNUM;
}
if (argc == 1) {
if (raw_smp_processor_id() != kdb_initial_cpu) {
kdb_printf("go <address> must be issued from the "
"initial cpu, do cpu %d first\n",
kdb_initial_cpu);
return KDB_ARGCOUNT;
}
nextarg = 1;
diag = kdbgetaddrarg(argc, argv, &nextarg,
&addr, &offset, NULL);