The patch titled
Subject: kgdb: timeout if secondary CPUs ignore the roundup
has been added to the -mm tree. Its filename is
kgdb-timeout-if-secondary-cpus-ignore-the-roundup.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/kgdb-timeout-if-secondary-cpus-ignore-the-roundup.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/kgdb-timeout-if-secondary-cpus-ignore-the-roundup.patch
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------------------------------------------------------
From: Daniel Thompson <daniel.thompson@xxxxxxxxxx>
Subject: kgdb: timeout if secondary CPUs ignore the roundup
Currently if an active CPU fails to respond to a roundup request the CPU
that requested the roundup will become stuck. This needlessly reduces the
robustness of the debugger.
This patch introduces a timeout allowing the system state to be examined
even when the system contains unresponsive processors. It also modifies
kdb's cpu command to make it censor attempts to switch to unresponsive
processors and to report their state as (D)ead.
Signed-off-by: Daniel Thompson <daniel.thompson@xxxxxxxxxx>
Cc: Jason Wessel <jason.wessel@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/debug/debug_core.c | 9 +++++++--
kernel/debug/kdb/kdb_debugger.c | 4 ++++
kernel/debug/kdb/kdb_main.c | 4 +++-
3 files changed, 14 insertions(+), 3 deletions(-)
diff -puN kernel/debug/debug_core.c~kgdb-timeout-if-secondary-cpus-ignore-the-roundup kernel/debug/debug_core.c
--- a/kernel/debug/debug_core.c~kgdb-timeout-if-secondary-cpus-ignore-the-roundup
+++ a/kernel/debug/debug_core.c
@@ -471,6 +471,7 @@ static int kgdb_cpu_enter(struct kgdb_st
int cpu;
int trace_on = 0;
int online_cpus = num_online_cpus();
+ u64 time_left;
kgdb_info[ks->cpu].enter_kgdb++;
kgdb_info[ks->cpu].exception_state |= exception_state;
@@ -595,9 +596,13 @@ return_normal:
/*
* Wait for the other CPUs to be notified and be waiting for us:
*/
- while (kgdb_do_roundup && (atomic_read(&masters_in_kgdb) +
- atomic_read(&slaves_in_kgdb)) != online_cpus)
+ time_left = loops_per_jiffy * HZ;
+ while (kgdb_do_roundup && --time_left &&
+ (atomic_read(&masters_in_kgdb) + atomic_read(&slaves_in_kgdb)) !=
+ online_cpus)
cpu_relax();
+ if (!time_left)
+ pr_crit("KGDB: Timed out waiting for secondary CPUs.\n");
/*
* At this point the primary processor is completely
diff -puN kernel/debug/kdb/kdb_debugger.c~kgdb-timeout-if-secondary-cpus-ignore-the-roundup kernel/debug/kdb/kdb_debugger.c
--- a/kernel/debug/kdb/kdb_debugger.c~kgdb-timeout-if-secondary-cpus-ignore-the-roundup
+++ a/kernel/debug/kdb/kdb_debugger.c
@@ -129,6 +129,10 @@ int kdb_stub(struct kgdb_state *ks)
ks->pass_exception = 1;
KDB_FLAG_SET(CATASTROPHIC);
}
+ /* set CATASTROPHIC if the system contains unresponsive processors */
+ for_each_online_cpu(i)
+ if (!kgdb_info[i].enter_kgdb)
+ KDB_FLAG_SET(CATASTROPHIC);
if (KDB_STATE(SSBPT) && reason == KDB_REASON_SSTEP) {
KDB_STATE_CLEAR(SSBPT);
KDB_STATE_CLEAR(DOING_SS);
diff -puN kernel/debug/kdb/kdb_main.c~kgdb-timeout-if-secondary-cpus-ignore-the-roundup kernel/debug/kdb/kdb_main.c
--- a/kernel/debug/kdb/kdb_main.c~kgdb-timeout-if-secondary-cpus-ignore-the-roundup
+++ a/kernel/debug/kdb/kdb_main.c
@@ -2157,6 +2157,8 @@ static void kdb_cpu_status(void)
for (start_cpu = -1, i = 0; i < NR_CPUS; i++) {
if (!cpu_online(i)) {
state = 'F'; /* cpu is offline */
+ } else if (!kgdb_info[i].enter_kgdb) {
+ state = 'D'; /* cpu is online but unresponsive */
} else {
state = ' '; /* cpu is responding to kdb */
if (kdb_task_state_char(KDB_TSK(i)) == 'I')
@@ -2210,7 +2212,7 @@ static int kdb_cpu(int argc, const char
/*
* Validate cpunum
*/
- if ((cpunum > NR_CPUS) || !cpu_online(cpunum))
+ if ((cpunum > NR_CPUS) || !kgdb_info[cpunum].enter_kgdb)
return KDB_BADCPUNUM;
dbg_switch_cpu = cpunum;
_
Patches currently in -mm which might be from daniel.thompson@xxxxxxxxxx are
kgdb-timeout-if-secondary-cpus-ignore-the-roundup.patch
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