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authorDaniel Thompson <daniel.thompson@linaro.org>2014-07-01 16:09:02 +0100
committerDaniel Thompson <daniel.thompson@linaro.org>2015-01-05 15:46:14 +0000
commit0493ee78434956f5d6e17b20eedfbf79e4f3814d (patch)
tree0d31484a98ee5b8e78a92f47f0e3948aa6b2850b
parent70691b13d2b7876ab50f68ccba1c604d9b181fb2 (diff)
downloadlinux-dev/kgdb-timeout.tar.gz
kgdb: Timeout if secondary CPUs ignore the roundupdev/kgdb-timeout
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@linaro.org> Cc: Jason Wessel <jason.wessel@windriver.com> Cc: Mike Travis <travis@sgi.com> Cc: Randy Dunlap <rdunlap@infradead.org> Cc: Dimitri Sivanich <sivanich@sgi.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Borislav Petkov <bp@suse.de> Cc: kgdb-bugreport@lists.sourceforge.net Cc: Ingo Molnar <mingo@kernel.org>
-rw-r--r--kernel/debug/debug_core.c9
-rw-r--r--kernel/debug/kdb/kdb_debugger.c4
-rw-r--r--kernel/debug/kdb/kdb_main.c4
3 files changed, 14 insertions, 3 deletions
diff --git a/kernel/debug/debug_core.c b/kernel/debug/debug_core.c
index 1adf62b39b96..f21580b347cc 100644
--- a/kernel/debug/debug_core.c
+++ b/kernel/debug/debug_core.c
@@ -471,6 +471,7 @@ static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs,
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("Timed out waiting for secondary CPUs.\n");
/*
* At this point the primary processor is completely
diff --git a/kernel/debug/kdb/kdb_debugger.c b/kernel/debug/kdb/kdb_debugger.c
index 8859ca34dcfe..15e1a7af5dd0 100644
--- a/kernel/debug/kdb/kdb_debugger.c
+++ b/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 --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c
index 379650b984f8..0c1dc7fa2e58 100644
--- a/kernel/debug/kdb/kdb_main.c
+++ b/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 **argv)
/*
* Validate cpunum
*/
- if ((cpunum > NR_CPUS) || !cpu_online(cpunum))
+ if ((cpunum >= CONFIG_NR_CPUS) || !kgdb_info[cpunum].enter_kgdb)
return KDB_BADCPUNUM;
dbg_switch_cpu = cpunum;