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 Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ 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 -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html