return unlikely(atomic_read(&panic_cpu) != PANIC_CPU_INVALID);
}
+ /* Return true if a panic is in progress on the current CPU. */
+ bool this_cpu_in_panic(void)
+ {
+ /*
+ * We can use raw_smp_processor_id() here because it is impossible for
+ * the task to be migrated to the panic_cpu, or away from it. If
+ * panic_cpu has already been set, and we're not currently executing on
+ * that CPU, then we never will be.
+ */
+ return unlikely(atomic_read(&panic_cpu) == raw_smp_processor_id());
+ }
+
+ /*
+ * Return true if a panic is in progress on a remote CPU.
+ *
+ * On true, the local CPU should immediately release any printing resources
+ * that may be needed by the panic CPU.
+ */
+ bool other_cpu_in_panic(void)
+ {
+ return (panic_in_progress() && !this_cpu_in_panic());
+ }
+
/*
* This is used for debugging the mess that is the VT code by
* keeping track if we have the console semaphore held. It's
static DEFINE_MUTEX(syslog_lock);
#ifdef CONFIG_PRINTK
- /*
- * During panic, heavy printk by other CPUs can delay the
- * panic and risk deadlock on console resources.
- */
- static int __read_mostly suppress_panic_printk;
-
DECLARE_WAIT_QUEUE_HEAD(log_wait);
/* All 3 protected by @syslog_lock. */
/* the next printk record to read by syslog(READ) or /proc/kmsg */
if (syslog_action_restricted(type)) {
if (capable(CAP_SYSLOG))
goto ok;
- /*
- * For historical reasons, accept CAP_SYS_ADMIN too, with
- * a warning.
- */
- if (capable(CAP_SYS_ADMIN)) {
- pr_warn_once("%s (%d): Attempt to access syslog with "
- "CAP_SYS_ADMIN but no CAP_SYSLOG "
- "(deprecated).\n",
- current->comm, task_pid_nr(current));
- goto ok;
- }
return -EPERM;
}
ok:
*/
static void console_lock_spinning_enable(void)
{
+ /*
+ * Do not use spinning in panic(). The panic CPU wants to keep the lock.
+ * Non-panic CPUs abandon the flush anyway.
+ *
+ * Just keep the lockdep annotation. The panic-CPU should avoid
+ * taking console_owner_lock because it might cause a deadlock.
+ * This looks like the easiest way how to prevent false lockdep
+ * reports without handling races a lockless way.
+ */
+ if (panic_in_progress())
+ goto lockdep;
+
raw_spin_lock(&console_owner_lock);
console_owner = current;
raw_spin_unlock(&console_owner_lock);
+ lockdep:
/* The waiter may spin on us after setting console_owner */
spin_acquire(&console_owner_dep_map, 0, 0, _THIS_IP_);
}
{
int waiter;
+ /*
+ * Ignore spinning waiters during panic() because they might get stopped
+ * or blocked at any time,
+ *
+ * It is safe because nobody is allowed to start spinning during panic
+ * in the first place. If there has been a waiter then non panic CPUs
+ * might stay spinning. They would get stopped anyway. The panic context
+ * will never start spinning and an interrupted spin on panic CPU will
+ * never continue.
+ */
+ if (panic_in_progress()) {
+ /* Keep lockdep happy. */
+ spin_release(&console_owner_dep_map, _THIS_IP_);
+ return 0;
+ }
+
raw_spin_lock(&console_owner_lock);
waiter = READ_ONCE(console_waiter);
console_owner = NULL;
if (unlikely(suppress_printk))
return 0;
- if (unlikely(suppress_panic_printk) &&
- atomic_read(&panic_cpu) != raw_smp_processor_id())
+ /*
+ * The messages on the panic CPU are the most important. If
+ * non-panic CPUs are generating any messages, they will be
+ * silently dropped.
+ */
+ if (other_cpu_in_panic())
return 0;
if (level == LOGLEVEL_SCHED) {
console_set_on_cmdline = 1;
}
-static int __add_preferred_console(char *name, int idx, char *options,
+static int __add_preferred_console(const char *name, const short idx, char *options,
char *brl_options, bool user_specified)
{
struct console_cmdline *c;
int i;
+ /*
+ * We use a signed short index for struct console for device drivers to
+ * indicate a not yet assigned index or port. However, a negative index
+ * value is not valid for preferred console.
+ */
+ if (idx < 0)
+ return -EINVAL;
+
/*
* See if this tty is not yet registered, and
* if we have a slot free.
* commonly to provide a default console (ie from PROM variables) when
* the user has not supplied one.
*/
-int add_preferred_console(char *name, int idx, char *options)
+int add_preferred_console(const char *name, const short idx, char *options)
{
return __add_preferred_console(name, idx, options, NULL, false);
}
return 0;
}
- /*
- * Return true if a panic is in progress on a remote CPU.
- *
- * On true, the local CPU should immediately release any printing resources
- * that may be needed by the panic CPU.
- */
- bool other_cpu_in_panic(void)
- {
- if (!panic_in_progress())
- return false;
-
- /*
- * We can use raw_smp_processor_id() here because it is impossible for
- * the task to be migrated to the panic_cpu, or away from it. If
- * panic_cpu has already been set, and we're not currently executing on
- * that CPU, then we never will be.
- */
- return atomic_read(&panic_cpu) != raw_smp_processor_id();
- }
-
/**
* console_lock - block the console subsystem from printing
*
bool printk_get_next_message(struct printk_message *pmsg, u64 seq,
bool is_extended, bool may_suppress)
{
- static int panic_console_dropped;
-
struct printk_buffers *pbufs = pmsg->pbufs;
const size_t scratchbuf_sz = sizeof(pbufs->scratchbuf);
const size_t outbuf_sz = sizeof(pbufs->outbuf);
pmsg->seq = r.info->seq;
pmsg->dropped = r.info->seq - seq;
- /*
- * Check for dropped messages in panic here so that printk
- * suppression can occur as early as possible if necessary.
- */
- if (pmsg->dropped &&
- panic_in_progress() &&
- panic_console_dropped++ > 10) {
- suppress_panic_printk = 1;
- pr_warn_once("Too many dropped messages. Suppress messages on non-panic CPUs to prevent livelock.\n");
- }
-
/* Skip record that has level above the console loglevel. */
if (may_suppress && suppress_message_printing(r.info->level))
goto out;
might_sleep();
- seq = prb_next_seq(prb);
+ seq = prb_next_reserve_seq(prb);
/* Flush the consoles so that records up to @seq are printed. */
console_lock();
projects / linux-2.6-microblaze.git / commitdiff