[PATCH] SW Breakpoint doesn't work after it triggers on non boot CPU

I'v set breakpoint to do_sync, then I'v triggered it, first on BOOT
CPU(CPU0), than on CPU1. Here is log:

[email protected]:~# sync
Instruction(i) breakpoint #0 at 0xc01787c1 (adjusted)
0xc01787c1 do_sync:         int3

Entering kdb (current=0xf7ce8ab0, pid 1718) on processor 0 due to Breakpoint @0xc01787c1
[0]kdb> go
[email protected]:~#
[email protected]:~#
[email protected]:~# taskset -c 1 sync
Instruction(i) breakpoint #0 at 0xc01787c1 (adjusted)
0xc01787c1 do_sync:         int3

Entering kdb (current=0xf7f81a30, pid 1719) on processor 1 due to Breakpoint @0xc01787c1
[1]kdb> go
[email protected]:~#
[email protected]:~#
[email protected]:~# sync
[email protected]:~#
[email protected]:~# sync
[email protected]:~#

Breakpoint on do_sync doesn't work after I've triggered it on the CPU1(taskset-c 1 sync).

The reasons of issue are:
1) code that related to install/remove global bp was hardwired to CPU with id
0, don't know why.
...
                if (!kdb_quiet(reason) || smp_processor_id() == 0) {
                        kdb_bp_install_global(regs);
                        kdbnearsym_cleanup();
                        debug_kusage();
                }
...
2) after single-step over a breakpoint KDB makes itself silent:
kdb()
...
        if (KDB_STATE(GO1)) {
                kdb_bp_remove_global();         /* They were set for
single-step purposes */
                KDB_STATE_CLEAR(GO1);
                reason = KDB_REASON_SILENT;     /* Now silently go */
        }
...
That prevents reinstall of global breakpoints when kernel is leaving kdb:
                /*
                 * (Re)install the global breakpoints and cleanup the cached
                 * symbol table.  This is only done once from the initial
                 * processor on go.
                 */
                KDB_DEBUG_STATE("kdb 12", reason);
                if (!kdb_quiet(reason) || smp_processor_id() == 0) {
                        kdb_bp_install_global(regs);
                        kdbnearsym_cleanup();
                        debug_kusage();
                }

How solved:
1) CPU0 code removed.
2) Patch checks if reason is set to KDB_REASON_SILENT and reinstall global
breakpoints in that case.
3) Also patch fixes KDB notifier when kernel exits KDB.

Patch was tested on x86_64 2 CPU PC with i386 2.6.21 kernel. Thanks.

Signed-off-by: Konstantin Baydarov <[email protected]>

 kdb/kdbmain.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

Index: linux-2.6.21/kdb/kdbmain.c
===================================================================
--- linux-2.6.21.orig/kdb/kdbmain.c
+++ linux-2.6.21/kdb/kdbmain.c
@@ -1974,7 +1974,7 @@ kdb(kdb_reason_t reason, int error, stru
 		 * Remove the global breakpoints.  This is only done
 		 * once from the initial processor on initial entry.
 		 */
-		if (!kdb_quiet(reason) || smp_processor_id() == 0)
+		if (!kdb_quiet(reason))
 			kdb_bp_remove_global();
 
 		/*
@@ -2028,7 +2028,7 @@ kdb(kdb_reason_t reason, int error, stru
 		 * processor on go.
 		 */
 		KDB_DEBUG_STATE("kdb 12", reason);
-		if (!kdb_quiet(reason) || smp_processor_id() == 0) {
+		if (!kdb_quiet(reason) || reason == KDB_REASON_SILENT) {
 			kdb_bp_install_global(regs);
 			kdbnearsym_cleanup();
 			debug_kusage();
@@ -2047,7 +2047,7 @@ kdb(kdb_reason_t reason, int error, stru
 			/* Wait until all the other processors leave kdb */
 			while (kdb_previous_event() != 1)
 				;
-			if (!kdb_quiet(reason))
+			if (!kdb_quiet(reason) || reason == KDB_REASON_SILENT)
 				notify_die(DIE_KDEBUG_LEAVE, "KDEBUG LEAVE", regs, error, 0, 0);
 			kdb_initial_cpu = -1;	/* release kdb control */
 			KDB_DEBUG_STATE("kdb 13", reason);
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