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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