This patch restores the capability to enter KDB (and KGDB) from the UV NMI handler. This is needed because the UV system console is not capable of sending the 'break' signal to the serial console port. It is also useful when the kernel is hung in such a way that it isn't responding to normal external I/O, so sending 'g' to sysreq-trigger does not work either. Another benefit of the external NMI command is that all the cpus receive the NMI signal at roughly the same time so they are more closely aligned timewise. It utilizes the newly added kgdb_nmicallin function to gain entry to KGDB/KDB by the master. The slaves still enter via the standard kgdb_nmicallback function. It also uses the new 'send_ready' pointer to tell KGDB/KDB to signal the slaves when to proceed into the KGDB slave loop. It is enabled when the nmi action is set to "kdb" and the kernel is built with CONFIG_KDB enabled. Signed-off-by: Mike Travis Reviewed-by: Dimitri Sivanich Reviewed-by: Hedi Berriche --- arch/x86/platform/uv/uv_nmi.c | 47 +++++++++++++++++++++++++++++++++++++++++- 1 file changed, 46 insertions(+), 1 deletion(-) --- linux.orig/arch/x86/platform/uv/uv_nmi.c +++ linux/arch/x86/platform/uv/uv_nmi.c @@ -21,7 +21,9 @@ #include #include +#include #include +#include #include #include #include @@ -32,6 +34,7 @@ #include #include #include +#include #include #include #include @@ -146,8 +149,9 @@ module_param_named(retry_count, uv_nmi_r * "dump" - dump process stack for each cpu * "ips" - dump IP info for each cpu * "kdump" - do crash dump + * "kdb" - enter KDB/KGDB (default) */ -static char uv_nmi_action[8] = "dump"; +static char uv_nmi_action[8] = "kdb"; module_param_string(action, uv_nmi_action, sizeof(uv_nmi_action), 0644); static inline bool uv_nmi_action_is(const char *action) @@ -533,6 +537,43 @@ static inline void uv_nmi_kdump(int cpu, } #endif /* !CONFIG_KEXEC */ +#ifdef CONFIG_KGDB_KDB +/* Call KDB from NMI handler */ +static void uv_call_kdb(int cpu, struct pt_regs *regs, int master) +{ + int ret; + + if (master) { + /* call KGDB NMI handler as MASTER */ + ret = kgdb_nmicallin(cpu, X86_TRAP_NMI, regs, + &uv_nmi_slave_continue); + if (ret) { + pr_alert("KDB returned error, is kgdboc set?\n"); + atomic_set(&uv_nmi_slave_continue, SLAVE_EXIT); + } + } else { + /* wait for KGDB signal that it's ready for slaves to enter */ + int sig; + + do { + cpu_relax(); + sig = atomic_read(&uv_nmi_slave_continue); + } while (!sig); + + /* call KGDB as slave */ + if (sig == SLAVE_CONTINUE) + ret = kgdb_nmicallback(cpu, regs); + } + uv_nmi_sync_exit(master); +} + +#else /* !CONFIG_KGDB_KDB */ +static inline void uv_call_kdb(int cpu, struct pt_regs *regs, int master) +{ + pr_err("UV: NMI error: KGDB/KDB is not enabled in this kernel\n"); +} +#endif /* !CONFIG_KGDB_KDB */ + /* * UV NMI handler */ @@ -565,6 +606,10 @@ int uv_handle_nmi(unsigned int reason, s if (uv_nmi_action_is("ips") || uv_nmi_action_is("dump")) uv_nmi_dump_state(cpu, regs, master); + /* Call KDB if enabled */ + else if (uv_nmi_action_is("kdb")) + uv_call_kdb(cpu, regs, master); + /* Clear per_cpu "in nmi" flag */ atomic_set(&uv_cpu_nmi.state, UV_NMI_STATE_OUT); -- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/