diff options
Diffstat (limited to 'arch/x86/kernel/cpu/mcheck/mce.c')
| -rw-r--r-- | arch/x86/kernel/cpu/mcheck/mce.c | 360 |
1 files changed, 331 insertions, 29 deletions
diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c index 421020f..ba43189 100644 --- a/arch/x86/kernel/cpu/mcheck/mce.c +++ b/arch/x86/kernel/cpu/mcheck/mce.c @@ -21,6 +21,7 @@ #include <linux/percpu.h> #include <linux/string.h> #include <linux/sysdev.h> +#include <linux/delay.h> #include <linux/ctype.h> #include <linux/sched.h> #include <linux/sysfs.h> @@ -28,6 +29,7 @@ #include <linux/init.h> #include <linux/kmod.h> #include <linux/poll.h> +#include <linux/nmi.h> #include <linux/cpu.h> #include <linux/smp.h> #include <linux/fs.h> @@ -60,6 +62,8 @@ int mce_disabled; #define MISC_MCELOG_MINOR 227 +#define SPINUNIT 100 /* 100ns */ + atomic_t mce_entry; DEFINE_PER_CPU(unsigned, mce_exception_count); @@ -77,6 +81,7 @@ static u64 *bank; static unsigned long notify_user; static int rip_msr; static int mce_bootlog = -1; +static int monarch_timeout = -1; static char trigger[128]; static char *trigger_argv[2] = { trigger, NULL }; @@ -84,6 +89,9 @@ static char *trigger_argv[2] = { trigger, NULL }; static unsigned long dont_init_banks; static DECLARE_WAIT_QUEUE_HEAD(mce_wait); +static DEFINE_PER_CPU(struct mce, mces_seen); +static int cpu_missing; + /* MCA banks polled by the period polling timer for corrected events */ DEFINE_PER_CPU(mce_banks_t, mce_poll_banks) = { @@ -241,6 +249,8 @@ static void mce_panic(char *msg, struct mce *final, char *exp) } if (final) print_mce(final); + if (cpu_missing) + printk(KERN_EMERG "Some CPUs didn't answer in synchronization\n"); if (exp) printk(KERN_EMERG "Machine check: %s\n", exp); panic(msg); @@ -451,18 +461,287 @@ static int mce_no_way_out(struct mce *m, char **msg) } /* + * Variable to establish order between CPUs while scanning. + * Each CPU spins initially until executing is equal its number. + */ +static atomic_t mce_executing; + +/* + * Defines order of CPUs on entry. First CPU becomes Monarch. + */ +static atomic_t mce_callin; + +/* + * Check if a timeout waiting for other CPUs happened. + */ +static int mce_timed_out(u64 *t) +{ + /* + * The others already did panic for some reason. + * Bail out like in a timeout. + * rmb() to tell the compiler that system_state + * might have been modified by someone else. + */ + rmb(); + if (atomic_read(&mce_paniced)) + wait_for_panic(); + if (!monarch_timeout) + goto out; + if ((s64)*t < SPINUNIT) { + /* CHECKME: Make panic default for 1 too? */ + if (tolerant < 1) + mce_panic("Timeout synchronizing machine check over CPUs", + NULL, NULL); + cpu_missing = 1; + return 1; + } + *t -= SPINUNIT; +out: + touch_nmi_watchdog(); + return 0; +} + +/* + * The Monarch's reign. The Monarch is the CPU who entered + * the machine check handler first. It waits for the others to + * raise the exception too and then grades them. When any + * error is fatal panic. Only then let the others continue. + * + * The other CPUs entering the MCE handler will be controlled by the + * Monarch. They are called Subjects. + * + * This way we prevent any potential data corruption in a unrecoverable case + * and also makes sure always all CPU's errors are examined. + * + * Also this detects the case of an machine check event coming from outer + * space (not detected by any CPUs) In this case some external agent wants + * us to shut down, so panic too. + * + * The other CPUs might still decide to panic if the handler happens + * in a unrecoverable place, but in this case the system is in a semi-stable + * state and won't corrupt anything by itself. It's ok to let the others + * continue for a bit first. + * + * All the spin loops have timeouts; when a timeout happens a CPU + * typically elects itself to be Monarch. + */ +static void mce_reign(void) +{ + int cpu; + struct mce *m = NULL; + int global_worst = 0; + char *msg = NULL; + char *nmsg = NULL; + + /* + * This CPU is the Monarch and the other CPUs have run + * through their handlers. + * Grade the severity of the errors of all the CPUs. + */ + for_each_possible_cpu(cpu) { + int severity = mce_severity(&per_cpu(mces_seen, cpu), tolerant, + &nmsg); + if (severity > global_worst) { + msg = nmsg; + global_worst = severity; + m = &per_cpu(mces_seen, cpu); + } + } + + /* + * Cannot recover? Panic here then. + * This dumps all the mces in the log buffer and stops the + * other CPUs. + */ + if (m && global_worst >= MCE_PANIC_SEVERITY && tolerant < 3) + mce_panic("Fatal machine check", m, msg); + + /* + * For UC somewhere we let the CPU who detects it handle it. + * Also must let continue the others, otherwise the handling + * CPU could deadlock on a lock. + */ + + /* + * No machine check event found. Must be some external + * source or one CPU is hung. Panic. + */ + if (!m && tolerant < 3) + mce_panic("Machine check from unknown source", NULL, NULL); + + /* + * Now clear all the mces_seen so that they don't reappear on + * the next mce. + */ + for_each_possible_cpu(cpu) + memset(&per_cpu(mces_seen, cpu), 0, sizeof(struct mce)); +} + +static atomic_t global_nwo; + +/* + * Start of Monarch synchronization. This waits until all CPUs have + * entered the exception handler and then determines if any of them + * saw a fatal event that requires panic. Then it executes them + * in the entry order. + * TBD double check parallel CPU hotunplug + */ +static int mce_start(int no_way_out, int *order) +{ + int nwo; + int cpus = num_online_cpus(); + u64 timeout = (u64)monarch_timeout * NSEC_PER_USEC; + + if (!timeout) { + *order = -1; + return no_way_out; + } + + atomic_add(no_way_out, &global_nwo); + + /* + * Wait for everyone. + */ + while (atomic_read(&mce_callin) != cpus) { + if (mce_timed_out(&timeout)) { + atomic_set(&global_nwo, 0); + *order = -1; + return no_way_out; + } + ndelay(SPINUNIT); + } + + /* + * Cache the global no_way_out state. + */ + nwo = atomic_read(&global_nwo); + + /* + * Monarch starts executing now, the others wait. + */ + if (*order == 1) { + atomic_set(&mce_executing, 1); + return nwo; + } + + /* + * Now start the scanning loop one by one + * in the original callin order. + * This way when there are any shared banks it will + * be only seen by one CPU before cleared, avoiding duplicates. + */ + while (atomic_read(&mce_executing) < *order) { + if (mce_timed_out(&timeout)) { + atomic_set(&global_nwo, 0); + *order = -1; + return no_way_out; + } + ndelay(SPINUNIT); + } + return nwo; +} + +/* + * Synchronize between CPUs after main scanning loop. + * This invokes the bulk of the Monarch processing. + */ +static int mce_end(int order) +{ + int ret = -1; + u64 timeout = (u64)monarch_timeout * NSEC_PER_USEC; + + if (!timeout) + goto reset; + if (order < 0) + goto reset; + + /* + * Allow others to run. + */ + atomic_inc(&mce_executing); + + if (order == 1) { + /* CHECKME: Can this race with a parallel hotplug? */ + int cpus = num_online_cpus(); + + /* + * Monarch: Wait for everyone to go through their scanning + * loops. + */ + while (atomic_read(&mce_executing) <= cpus) { + if (mce_timed_out(&timeout)) + goto reset; + ndelay(SPINUNIT); + } + + mce_reign(); + barrier(); + ret = 0; + } else { + /* + * Subject: Wait for Monarch to finish. + */ + while (atomic_read(&mce_executing) != 0) { + if (mce_timed_out(&timeout)) + goto reset; + ndelay(SPINUNIT); + } + + /* + * Don't reset anything. That's done by the Monarch. + */ + return 0; + } + + /* + * Reset all global state. + */ +reset: + atomic_set(&global_nwo, 0); + atomic_set(&mce_callin, 0); + barrier(); + + /* + * Let others run again. + */ + atomic_set(&mce_executing, 0); + return ret; +} + +static void mce_clear_state(unsigned long *toclear) +{ + int i; + + for (i = 0; i < banks; i++) { + if (test_bit(i, toclear)) + mce_wrmsrl(MSR_IA32_MC0_STATUS+4*i, 0); + } +} + +/* * The actual machine check handler. This only handles real * exceptions when something got corrupted coming in through int 18. * * This is executed in NMI context not subject to normal locking rules. This * implies that most kernel services cannot be safely used. Don't even * think about putting a printk in there! + * + * On Intel systems this is entered on all CPUs in parallel through + * MCE broadcast. However some CPUs might be broken beyond repair, + * so be always careful when synchronizing with others. */ void do_machine_check(struct pt_regs *regs, long error_code) { - struct mce m, panicm; - int panicm_found = 0; + struct mce m, *final; int i; + int worst = 0; + int severity; + /* + * Establish sequential order between the CPUs entering the machine + * check handler. + */ + int order; + /* * If no_way_out gets set, there is no safe way to recover from this * MCE. If tolerant is cranked up, we'll try anyway. @@ -486,13 +765,23 @@ void do_machine_check(struct pt_regs *regs, long error_code) if (!banks) goto out; + order = atomic_add_return(1, &mce_callin); mce_setup(&m); m.mcgstatus = mce_rdmsrl(MSR_IA32_MCG_STATUS); no_way_out = mce_no_way_out(&m, &msg); + final = &__get_cpu_var(mces_seen); + *final = m; + barrier(); + /* + * Go through all the banks in exclusion of the other CPUs. + * This way we don't report duplicated events on shared banks + * because the first one to see it will clear it. + */ + no_way_out = mce_start(no_way_out, &order); for (i = 0; i < banks; i++) { __clear_bit(i, toclear); if (!bank[i]) @@ -544,32 +833,32 @@ void do_machine_check(struct pt_regs *regs, long error_code) mce_get_rip(&m, regs); mce_log(&m); - /* - * Did this bank cause the exception? - * - * Assume that the bank with uncorrectable errors did it, - * and that there is only a single one: - */ - if ((m.status & MCI_STATUS_UC) && - (m.status & MCI_STATUS_EN)) { - panicm = m; - panicm_found = 1; + severity = mce_severity(&m, tolerant, NULL); + if (severity > worst) { + *final = m; + worst = severity; } } + if (!no_way_out) + mce_clear_state(toclear); + /* - * If we didn't find an uncorrectable error, pick - * the last one (shouldn't happen, just being safe). + * Do most of the synchronization with other CPUs. + * When there's any problem use only local no_way_out state. */ - if (!panicm_found) - panicm = m; + if (mce_end(order) < 0) + no_way_out = worst >= MCE_PANIC_SEVERITY; /* * If we have decided that we just CAN'T continue, and the user * has not set tolerant to an insane level, give up and die. + * + * This is mainly used in the case when the system doesn't + * support MCE broadcasting or it has been disabled. */ if (no_way_out && tolerant < 3) - mce_panic("Machine check", &panicm, msg); + mce_panic("Machine check", final, msg); /* * If the error seems to be unrecoverable, something should be @@ -585,7 +874,7 @@ void do_machine_check(struct pt_regs *regs, long error_code) * instruction which caused the MCE. */ if (m.mcgstatus & MCG_STATUS_EIPV) - user_space = panicm.ip && (panicm.cs & 3); + user_space = final->ip && (final->cs & 3); /* * If we know that the error was in user space, send a @@ -597,20 +886,15 @@ void do_machine_check(struct pt_regs *regs, long error_code) if (user_space) { force_sig(SIGBUS, current); } else if (panic_on_oops || tolerant < 2) { - mce_panic("Uncorrected machine check", &panicm, msg); + mce_panic("Uncorrected machine check", final, msg); } } /* notify userspace ASAP */ set_thread_flag(TIF_MCE_NOTIFY); - mce_report_event(regs); - - /* the last thing we do is clear state */ - for (i = 0; i < banks; i++) { - if (test_bit(i, toclear)) - mce_wrmsrl(MSR_IA32_MC0_STATUS+4*i, 0); - } + if (worst > 0) + mce_report_event(regs); mce_wrmsrl(MSR_IA32_MCG_STATUS, 0); out: atomic_dec(&mce_entry); @@ -821,7 +1105,17 @@ static void mce_cpu_quirks(struct cpuinfo_x86 *c) if (c->x86 == 6 && c->x86_model < 0x1A) __set_bit(0, &dont_init_banks); + + /* + * All newer Intel systems support MCE broadcasting. Enable + * synchronization with a one second timeout. + */ + if ((c->x86 > 6 || (c->x86 == 6 && c->x86_model >= 0xe)) && + monarch_timeout < 0) + monarch_timeout = USEC_PER_SEC; } + if (monarch_timeout < 0) + monarch_timeout = 0; } static void __cpuinit mce_ancient_init(struct cpuinfo_x86 *c) @@ -1068,7 +1362,9 @@ static struct miscdevice mce_log_device = { /* * mce=off disables machine check - * mce=TOLERANCELEVEL (number, see above) + * mce=TOLERANCELEVEL[,monarchtimeout] (number, see above) + * monarchtimeout is how long to wait for other CPUs on machine + * check, or 0 to not wait * mce=bootlog Log MCEs from before booting. Disabled by default on AMD. * mce=nobootlog Don't log MCEs from before booting. */ @@ -1082,9 +1378,13 @@ static int __init mcheck_enable(char *str) mce_disabled = 1; else if (!strcmp(str, "bootlog") || !strcmp(str, "nobootlog")) mce_bootlog = (str[0] == 'b'); - else if (isdigit(str[0])) + else if (isdigit(str[0])) { get_option(&str, &tolerant); - else { + if (*str == ',') { + ++str; + get_option(&str, &monarch_timeout); + } + } else { printk(KERN_INFO "mce argument %s ignored. Please use /sys\n", str); return 0; @@ -1221,6 +1521,7 @@ static ssize_t store_int_with_restart(struct sys_device *s, static SYSDEV_ATTR(trigger, 0644, show_trigger, set_trigger); static SYSDEV_INT_ATTR(tolerant, 0644, tolerant); +static SYSDEV_INT_ATTR(monarch_timeout, 0644, monarch_timeout); static struct sysdev_ext_attribute attr_check_interval = { _SYSDEV_ATTR(check_interval, 0644, sysdev_show_int, @@ -1230,6 +1531,7 @@ static struct sysdev_ext_attribute attr_check_interval = { static struct sysdev_attribute *mce_attrs[] = { &attr_tolerant.attr, &attr_check_interval.attr, &attr_trigger, + &attr_monarch_timeout.attr, NULL }; |
