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>
diff --git a/kernel/debug/debug_core.c b/kernel/debug/debug_core.c
index 26dbdc3..fec596d 100644
--- a/kernel/debug/debug_core.c
+++ b/kernel/debug/debug_core.c
@@ -460,19 +460,6 @@
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 @@
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;
diff --git a/kernel/debug/kdb/kdb_debugger.c b/kernel/debug/kdb/kdb_debugger.c
index bf6e827..dd0b1b7 100644
--- a/kernel/debug/kdb/kdb_debugger.c
+++ b/kernel/debug/kdb/kdb_debugger.c
@@ -86,7 +86,7 @@
}
/* 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 @@
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);
diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c
index 4226f32..d7bda21 100644
--- a/kernel/debug/kdb/kdb_main.c
+++ b/kernel/debug/kdb/kdb_main.c
@@ -1749,13 +1749,13 @@
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);