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Commit 495363d3 authored by Jason Wessel's avatar Jason Wessel
Browse files

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: default avatarJason Wessel <jason.wessel@windriver.com>
parent dfee3a7b

kernel/debug/debug_core.c

+2 −14
Original line number Diff line number Diff line
@@ -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 @@ static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs, 
		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;

kernel/debug/kdb/kdb_debugger.c

+1 −2
Original line number Diff line number Diff line
@@ -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);

kernel/debug/kdb/kdb_main.c

+6 −6
Original line number Diff line number Diff line
@@ -1749,13 +1749,13 @@ static int kdb_go(int argc, const char **argv) 
	int nextarg;

	long offset;



	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_printf("go must execute on the entry cpu, "

			   "please use \"cpu %d\" and then execute go\n",

			   kdb_initial_cpu);

			return KDB_ARGCOUNT;

		return KDB_BADCPUNUM;

	}

	if (argc == 1) {

		nextarg = 1;

		diag = kdbgetaddrarg(argc, argv, &nextarg,

				     &addr, &offset, NULL);