printk changes for 6.9
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Merge tag 'printk-for-6.9' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux
Pull printk updates from Petr Mladek:
"Improve the behavior during panic. The issues were found when testing
the ongoing changes introducing atomic consoles and printk kthreads:
- pr_flush() has to wait for the last reserved record instead of the
last finalized one. Note that records are finalized in random order
when generated by more CPUs in parallel.
- Ignore non-finalized records during panic(). Messages printed on
panic-CPU are always finalized. Messages printed by other CPUs
might never be finalized when the CPUs get stopped.
- Block new printk() calls on non-panic CPUs completely. Backtraces
are printed before entering the panic mode. Later messages would
just mess information printed by the panic CPU.
- Do not take console_lock in console_flush_on_panic() at all. The
original code did try_lock()/console_unlock(). The unlock part
might cause a deadlock when panic() happened in a scheduler code.
- Fix conversion of 64-bit sequence number for 32-bit atomic
operations"
* tag 'printk-for-6.9' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux:
dump_stack: Do not get cpu_sync for panic CPU
panic: Flush kernel log buffer at the end
printk: Avoid non-panic CPUs writing to ringbuffer
printk: Disable passing console lock owner completely during panic()
printk: ringbuffer: Skip non-finalized records in panic
printk: Wait for all reserved records with pr_flush()
printk: ringbuffer: Cleanup reader terminology
printk: Add this_cpu_in_panic()
printk: For @suppress_panic_printk check for other CPU in panic
printk: ringbuffer: Clarify special lpos values
printk: ringbuffer: Do not skip non-finalized records with prb_next_seq()
printk: Use prb_first_seq() as base for 32bit seq macros
printk: Adjust mapping for 32bit seq macros
printk: nbcon: Relocate 32bit seq macros
This commit is contained in:
Linus Torvalds
commit
b0546776ad
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@ -273,6 +273,8 @@ static inline void printk_trigger_flush(void)
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}
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#endif
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bool this_cpu_in_panic(void);
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#ifdef CONFIG_SMP
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extern int __printk_cpu_sync_try_get(void);
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extern void __printk_cpu_sync_wait(void);
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@ -446,6 +446,14 @@ void panic(const char *fmt, ...)
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/* Do not scroll important messages printed above */
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suppress_printk = 1;
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/*
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* The final messages may not have been printed if in a context that
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* defers printing (such as NMI) and irq_work is not available.
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* Explicitly flush the kernel log buffer one last time.
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*/
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console_flush_on_panic(CONSOLE_FLUSH_PENDING);
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local_irq_enable();
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for (i = 0; ; i += PANIC_TIMER_STEP) {
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touch_softlockup_watchdog();
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@ -140,39 +140,6 @@ static inline bool nbcon_state_try_cmpxchg(struct console *con, struct nbcon_sta
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return atomic_try_cmpxchg(&ACCESS_PRIVATE(con, nbcon_state), &cur->atom, new->atom);
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}
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#ifdef CONFIG_64BIT
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#define __seq_to_nbcon_seq(seq) (seq)
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#define __nbcon_seq_to_seq(seq) (seq)
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#else /* CONFIG_64BIT */
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#define __seq_to_nbcon_seq(seq) ((u32)seq)
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static inline u64 __nbcon_seq_to_seq(u32 nbcon_seq)
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{
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u64 seq;
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u64 rb_next_seq;
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/*
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* The provided sequence is only the lower 32 bits of the ringbuffer
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* sequence. It needs to be expanded to 64bit. Get the next sequence
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* number from the ringbuffer and fold it.
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*
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* Having a 32bit representation in the console is sufficient.
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* If a console ever gets more than 2^31 records behind
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* the ringbuffer then this is the least of the problems.
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*
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* Also the access to the ring buffer is always safe.
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*/
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rb_next_seq = prb_next_seq(prb);
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seq = rb_next_seq - ((u32)rb_next_seq - nbcon_seq);
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return seq;
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}
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#endif /* CONFIG_64BIT */
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/**
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* nbcon_seq_read - Read the current console sequence
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* @con: Console to read the sequence of
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@ -183,7 +150,7 @@ u64 nbcon_seq_read(struct console *con)
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{
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unsigned long nbcon_seq = atomic_long_read(&ACCESS_PRIVATE(con, nbcon_seq));
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return __nbcon_seq_to_seq(nbcon_seq);
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return __ulseq_to_u64seq(prb, nbcon_seq);
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}
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/**
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@ -204,7 +171,7 @@ void nbcon_seq_force(struct console *con, u64 seq)
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*/
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u64 valid_seq = max_t(u64, seq, prb_first_valid_seq(prb));
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atomic_long_set(&ACCESS_PRIVATE(con, nbcon_seq), __seq_to_nbcon_seq(valid_seq));
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atomic_long_set(&ACCESS_PRIVATE(con, nbcon_seq), __u64seq_to_ulseq(valid_seq));
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/* Clear con->seq since nbcon consoles use con->nbcon_seq instead. */
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con->seq = 0;
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@ -223,11 +190,11 @@ void nbcon_seq_force(struct console *con, u64 seq)
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*/
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static void nbcon_seq_try_update(struct nbcon_context *ctxt, u64 new_seq)
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{
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unsigned long nbcon_seq = __seq_to_nbcon_seq(ctxt->seq);
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unsigned long nbcon_seq = __u64seq_to_ulseq(ctxt->seq);
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struct console *con = ctxt->console;
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if (atomic_long_try_cmpxchg(&ACCESS_PRIVATE(con, nbcon_seq), &nbcon_seq,
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__seq_to_nbcon_seq(new_seq))) {
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__u64seq_to_ulseq(new_seq))) {
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ctxt->seq = new_seq;
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} else {
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ctxt->seq = nbcon_seq_read(con);
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@ -347,6 +347,29 @@ static bool panic_in_progress(void)
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return unlikely(atomic_read(&panic_cpu) != PANIC_CPU_INVALID);
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}
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/* Return true if a panic is in progress on the current CPU. */
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bool this_cpu_in_panic(void)
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{
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/*
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* We can use raw_smp_processor_id() here because it is impossible for
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* the task to be migrated to the panic_cpu, or away from it. If
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* panic_cpu has already been set, and we're not currently executing on
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* that CPU, then we never will be.
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*/
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return unlikely(atomic_read(&panic_cpu) == raw_smp_processor_id());
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}
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/*
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* Return true if a panic is in progress on a remote CPU.
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*
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* On true, the local CPU should immediately release any printing resources
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* that may be needed by the panic CPU.
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*/
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bool other_cpu_in_panic(void)
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{
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return (panic_in_progress() && !this_cpu_in_panic());
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}
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/*
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* This is used for debugging the mess that is the VT code by
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* keeping track if we have the console semaphore held. It's
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@ -439,12 +462,6 @@ static int console_msg_format = MSG_FORMAT_DEFAULT;
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static DEFINE_MUTEX(syslog_lock);
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#ifdef CONFIG_PRINTK
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/*
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* During panic, heavy printk by other CPUs can delay the
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* panic and risk deadlock on console resources.
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*/
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static int __read_mostly suppress_panic_printk;
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DECLARE_WAIT_QUEUE_HEAD(log_wait);
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/* All 3 protected by @syslog_lock. */
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/* the next printk record to read by syslog(READ) or /proc/kmsg */
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@ -1835,10 +1852,23 @@ static bool console_waiter;
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*/
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static void console_lock_spinning_enable(void)
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{
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/*
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* Do not use spinning in panic(). The panic CPU wants to keep the lock.
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* Non-panic CPUs abandon the flush anyway.
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*
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* Just keep the lockdep annotation. The panic-CPU should avoid
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* taking console_owner_lock because it might cause a deadlock.
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* This looks like the easiest way how to prevent false lockdep
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* reports without handling races a lockless way.
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*/
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if (panic_in_progress())
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goto lockdep;
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raw_spin_lock(&console_owner_lock);
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console_owner = current;
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raw_spin_unlock(&console_owner_lock);
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lockdep:
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/* The waiter may spin on us after setting console_owner */
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spin_acquire(&console_owner_dep_map, 0, 0, _THIS_IP_);
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}
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@ -1863,6 +1893,22 @@ static int console_lock_spinning_disable_and_check(int cookie)
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{
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int waiter;
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/*
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* Ignore spinning waiters during panic() because they might get stopped
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* or blocked at any time,
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*
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* It is safe because nobody is allowed to start spinning during panic
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* in the first place. If there has been a waiter then non panic CPUs
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* might stay spinning. They would get stopped anyway. The panic context
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* will never start spinning and an interrupted spin on panic CPU will
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* never continue.
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*/
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if (panic_in_progress()) {
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/* Keep lockdep happy. */
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spin_release(&console_owner_dep_map, _THIS_IP_);
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return 0;
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}
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raw_spin_lock(&console_owner_lock);
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waiter = READ_ONCE(console_waiter);
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console_owner = NULL;
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@ -2259,8 +2305,12 @@ asmlinkage int vprintk_emit(int facility, int level,
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if (unlikely(suppress_printk))
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return 0;
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if (unlikely(suppress_panic_printk) &&
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atomic_read(&panic_cpu) != raw_smp_processor_id())
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/*
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* The messages on the panic CPU are the most important. If
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* non-panic CPUs are generating any messages, they will be
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* silently dropped.
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*/
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if (other_cpu_in_panic())
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return 0;
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if (level == LOGLEVEL_SCHED) {
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@ -2590,26 +2640,6 @@ static int console_cpu_notify(unsigned int cpu)
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return 0;
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}
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/*
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* Return true if a panic is in progress on a remote CPU.
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*
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* On true, the local CPU should immediately release any printing resources
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* that may be needed by the panic CPU.
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*/
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bool other_cpu_in_panic(void)
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{
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if (!panic_in_progress())
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return false;
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/*
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* We can use raw_smp_processor_id() here because it is impossible for
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* the task to be migrated to the panic_cpu, or away from it. If
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* panic_cpu has already been set, and we're not currently executing on
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* that CPU, then we never will be.
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*/
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return atomic_read(&panic_cpu) != raw_smp_processor_id();
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}
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/**
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* console_lock - block the console subsystem from printing
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*
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@ -2765,8 +2795,6 @@ void console_prepend_dropped(struct printk_message *pmsg, unsigned long dropped)
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bool printk_get_next_message(struct printk_message *pmsg, u64 seq,
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bool is_extended, bool may_suppress)
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{
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static int panic_console_dropped;
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struct printk_buffers *pbufs = pmsg->pbufs;
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const size_t scratchbuf_sz = sizeof(pbufs->scratchbuf);
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const size_t outbuf_sz = sizeof(pbufs->outbuf);
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@ -2794,17 +2822,6 @@ bool printk_get_next_message(struct printk_message *pmsg, u64 seq,
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pmsg->seq = r.info->seq;
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pmsg->dropped = r.info->seq - seq;
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/*
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* Check for dropped messages in panic here so that printk
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* suppression can occur as early as possible if necessary.
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*/
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if (pmsg->dropped &&
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panic_in_progress() &&
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panic_console_dropped++ > 10) {
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suppress_panic_printk = 1;
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pr_warn_once("Too many dropped messages. Suppress messages on non-panic CPUs to prevent livelock.\n");
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}
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/* Skip record that has level above the console loglevel. */
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if (may_suppress && suppress_message_printing(r.info->level))
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goto out;
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@ -3750,7 +3767,7 @@ static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progre
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might_sleep();
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seq = prb_next_seq(prb);
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seq = prb_next_reserve_seq(prb);
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/* Flush the consoles so that records up to @seq are printed. */
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console_lock();
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@ -6,6 +6,7 @@
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#include <linux/errno.h>
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#include <linux/bug.h>
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#include "printk_ringbuffer.h"
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#include "internal.h"
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/**
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* DOC: printk_ringbuffer overview
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@ -303,6 +304,9 @@
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*
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* desc_push_tail:B / desc_reserve:D
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* set descriptor reusable (state), then push descriptor tail (id)
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*
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* desc_update_last_finalized:A / desc_last_finalized_seq:A
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* store finalized record, then set new highest finalized sequence number
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*/
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#define DATA_SIZE(data_ring) _DATA_SIZE((data_ring)->size_bits)
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@ -1030,9 +1034,13 @@ static char *data_alloc(struct printk_ringbuffer *rb, unsigned int size,
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unsigned long next_lpos;
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if (size == 0) {
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/* Specify a data-less block. */
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blk_lpos->begin = NO_LPOS;
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blk_lpos->next = NO_LPOS;
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/*
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* Data blocks are not created for empty lines. Instead, the
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* reader will recognize these special lpos values and handle
|
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* it appropriately.
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*/
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blk_lpos->begin = EMPTY_LINE_LPOS;
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blk_lpos->next = EMPTY_LINE_LPOS;
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return NULL;
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}
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@ -1210,10 +1218,18 @@ static const char *get_data(struct prb_data_ring *data_ring,
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/* Data-less data block description. */
|
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if (BLK_DATALESS(blk_lpos)) {
|
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if (blk_lpos->begin == NO_LPOS && blk_lpos->next == NO_LPOS) {
|
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/*
|
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* Records that are just empty lines are also valid, even
|
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* though they do not have a data block. For such records
|
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* explicitly return empty string data to signify success.
|
||||
*/
|
||||
if (blk_lpos->begin == EMPTY_LINE_LPOS &&
|
||||
blk_lpos->next == EMPTY_LINE_LPOS) {
|
||||
*data_size = 0;
|
||||
return "";
|
||||
}
|
||||
|
||||
/* Data lost, invalid, or otherwise unavailable. */
|
||||
return NULL;
|
||||
}
|
||||
|
||||
|
|
@ -1441,20 +1457,118 @@ fail_reopen:
|
|||
return false;
|
||||
}
|
||||
|
||||
/*
|
||||
* @last_finalized_seq value guarantees that all records up to and including
|
||||
* this sequence number are finalized and can be read. The only exception are
|
||||
* too old records which have already been overwritten.
|
||||
*
|
||||
* It is also guaranteed that @last_finalized_seq only increases.
|
||||
*
|
||||
* Be aware that finalized records following non-finalized records are not
|
||||
* reported because they are not yet available to the reader. For example,
|
||||
* a new record stored via printk() will not be available to a printer if
|
||||
* it follows a record that has not been finalized yet. However, once that
|
||||
* non-finalized record becomes finalized, @last_finalized_seq will be
|
||||
* appropriately updated and the full set of finalized records will be
|
||||
* available to the printer. And since each printk() caller will either
|
||||
* directly print or trigger deferred printing of all available unprinted
|
||||
* records, all printk() messages will get printed.
|
||||
*/
|
||||
static u64 desc_last_finalized_seq(struct printk_ringbuffer *rb)
|
||||
{
|
||||
struct prb_desc_ring *desc_ring = &rb->desc_ring;
|
||||
unsigned long ulseq;
|
||||
|
||||
/*
|
||||
* Guarantee the sequence number is loaded before loading the
|
||||
* associated record in order to guarantee that the record can be
|
||||
* seen by this CPU. This pairs with desc_update_last_finalized:A.
|
||||
*/
|
||||
ulseq = atomic_long_read_acquire(&desc_ring->last_finalized_seq
|
||||
); /* LMM(desc_last_finalized_seq:A) */
|
||||
|
||||
return __ulseq_to_u64seq(rb, ulseq);
|
||||
}
|
||||
|
||||
static bool _prb_read_valid(struct printk_ringbuffer *rb, u64 *seq,
|
||||
struct printk_record *r, unsigned int *line_count);
|
||||
|
||||
/*
|
||||
* Check if there are records directly following @last_finalized_seq that are
|
||||
* finalized. If so, update @last_finalized_seq to the latest of these
|
||||
* records. It is not allowed to skip over records that are not yet finalized.
|
||||
*/
|
||||
static void desc_update_last_finalized(struct printk_ringbuffer *rb)
|
||||
{
|
||||
struct prb_desc_ring *desc_ring = &rb->desc_ring;
|
||||
u64 old_seq = desc_last_finalized_seq(rb);
|
||||
unsigned long oldval;
|
||||
unsigned long newval;
|
||||
u64 finalized_seq;
|
||||
u64 try_seq;
|
||||
|
||||
try_again:
|
||||
finalized_seq = old_seq;
|
||||
try_seq = finalized_seq + 1;
|
||||
|
||||
/* Try to find later finalized records. */
|
||||
while (_prb_read_valid(rb, &try_seq, NULL, NULL)) {
|
||||
finalized_seq = try_seq;
|
||||
try_seq++;
|
||||
}
|
||||
|
||||
/* No update needed if no later finalized record was found. */
|
||||
if (finalized_seq == old_seq)
|
||||
return;
|
||||
|
||||
oldval = __u64seq_to_ulseq(old_seq);
|
||||
newval = __u64seq_to_ulseq(finalized_seq);
|
||||
|
||||
/*
|
||||
* Set the sequence number of a later finalized record that has been
|
||||
* seen.
|
||||
*
|
||||
* Guarantee the record data is visible to other CPUs before storing
|
||||
* its sequence number. This pairs with desc_last_finalized_seq:A.
|
||||
*
|
||||
* Memory barrier involvement:
|
||||
*
|
||||
* If desc_last_finalized_seq:A reads from
|
||||
* desc_update_last_finalized:A, then desc_read:A reads from
|
||||
* _prb_commit:B.
|
||||
*
|
||||
* Relies on:
|
||||
*
|
||||
* RELEASE from _prb_commit:B to desc_update_last_finalized:A
|
||||
* matching
|
||||
* ACQUIRE from desc_last_finalized_seq:A to desc_read:A
|
||||
*
|
||||
* Note: _prb_commit:B and desc_update_last_finalized:A can be
|
||||
* different CPUs. However, the desc_update_last_finalized:A
|
||||
* CPU (which performs the release) must have previously seen
|
||||
* _prb_commit:B.
|
||||
*/
|
||||
if (!atomic_long_try_cmpxchg_release(&desc_ring->last_finalized_seq,
|
||||
&oldval, newval)) { /* LMM(desc_update_last_finalized:A) */
|
||||
old_seq = __ulseq_to_u64seq(rb, oldval);
|
||||
goto try_again;
|
||||
}
|
||||
}
|
||||
|
||||
/*
|
||||
* Attempt to finalize a specified descriptor. If this fails, the descriptor
|
||||
* is either already final or it will finalize itself when the writer commits.
|
||||
*/
|
||||
static void desc_make_final(struct prb_desc_ring *desc_ring, unsigned long id)
|
||||
static void desc_make_final(struct printk_ringbuffer *rb, unsigned long id)
|
||||
{
|
||||
struct prb_desc_ring *desc_ring = &rb->desc_ring;
|
||||
unsigned long prev_state_val = DESC_SV(id, desc_committed);
|
||||
struct prb_desc *d = to_desc(desc_ring, id);
|
||||
|
||||
atomic_long_cmpxchg_relaxed(&d->state_var, prev_state_val,
|
||||
DESC_SV(id, desc_finalized)); /* LMM(desc_make_final:A) */
|
||||
|
||||
/* Best effort to remember the last finalized @id. */
|
||||
atomic_long_set(&desc_ring->last_finalized_id, id);
|
||||
if (atomic_long_try_cmpxchg_relaxed(&d->state_var, &prev_state_val,
|
||||
DESC_SV(id, desc_finalized))) { /* LMM(desc_make_final:A) */
|
||||
desc_update_last_finalized(rb);
|
||||
}
|
||||
}
|
||||
|
||||
/**
|
||||
|
|
@ -1550,7 +1664,7 @@ bool prb_reserve(struct prb_reserved_entry *e, struct printk_ringbuffer *rb,
|
|||
* readers. (For seq==0 there is no previous descriptor.)
|
||||
*/
|
||||
if (info->seq > 0)
|
||||
desc_make_final(desc_ring, DESC_ID(id - 1));
|
||||
desc_make_final(rb, DESC_ID(id - 1));
|
||||
|
||||
r->text_buf = data_alloc(rb, r->text_buf_size, &d->text_blk_lpos, id);
|
||||
/* If text data allocation fails, a data-less record is committed. */
|
||||
|
|
@ -1643,7 +1757,7 @@ void prb_commit(struct prb_reserved_entry *e)
|
|||
*/
|
||||
head_id = atomic_long_read(&desc_ring->head_id); /* LMM(prb_commit:A) */
|
||||
if (head_id != e->id)
|
||||
desc_make_final(desc_ring, e->id);
|
||||
desc_make_final(e->rb, e->id);
|
||||
}
|
||||
|
||||
/**
|
||||
|
|
@ -1663,12 +1777,9 @@ void prb_commit(struct prb_reserved_entry *e)
|
|||
*/
|
||||
void prb_final_commit(struct prb_reserved_entry *e)
|
||||
{
|
||||
struct prb_desc_ring *desc_ring = &e->rb->desc_ring;
|
||||
|
||||
_prb_commit(e, desc_finalized);
|
||||
|
||||
/* Best effort to remember the last finalized @id. */
|
||||
atomic_long_set(&desc_ring->last_finalized_id, e->id);
|
||||
desc_update_last_finalized(e->rb);
|
||||
}
|
||||
|
||||
/*
|
||||
|
|
@ -1832,7 +1943,7 @@ static int prb_read(struct printk_ringbuffer *rb, u64 seq,
|
|||
}
|
||||
|
||||
/* Get the sequence number of the tail descriptor. */
|
||||
static u64 prb_first_seq(struct printk_ringbuffer *rb)
|
||||
u64 prb_first_seq(struct printk_ringbuffer *rb)
|
||||
{
|
||||
struct prb_desc_ring *desc_ring = &rb->desc_ring;
|
||||
enum desc_state d_state;
|
||||
|
|
@ -1875,12 +1986,123 @@ static u64 prb_first_seq(struct printk_ringbuffer *rb)
|
|||
return seq;
|
||||
}
|
||||
|
||||
/*
|
||||
* Non-blocking read of a record. Updates @seq to the last finalized record
|
||||
* (which may have no data available).
|
||||
/**
|
||||
* prb_next_reserve_seq() - Get the sequence number after the most recently
|
||||
* reserved record.
|
||||
*
|
||||
* See the description of prb_read_valid() and prb_read_valid_info()
|
||||
* for details.
|
||||
* @rb: The ringbuffer to get the sequence number from.
|
||||
*
|
||||
* This is the public function available to readers to see what sequence
|
||||
* number will be assigned to the next reserved record.
|
||||
*
|
||||
* Note that depending on the situation, this value can be equal to or
|
||||
* higher than the sequence number returned by prb_next_seq().
|
||||
*
|
||||
* Context: Any context.
|
||||
* Return: The sequence number that will be assigned to the next record
|
||||
* reserved.
|
||||
*/
|
||||
u64 prb_next_reserve_seq(struct printk_ringbuffer *rb)
|
||||
{
|
||||
struct prb_desc_ring *desc_ring = &rb->desc_ring;
|
||||
unsigned long last_finalized_id;
|
||||
atomic_long_t *state_var;
|
||||
u64 last_finalized_seq;
|
||||
unsigned long head_id;
|
||||
struct prb_desc desc;
|
||||
unsigned long diff;
|
||||
struct prb_desc *d;
|
||||
int err;
|
||||
|
||||
/*
|
||||
* It may not be possible to read a sequence number for @head_id.
|
||||
* So the ID of @last_finailzed_seq is used to calculate what the
|
||||
* sequence number of @head_id will be.
|
||||
*/
|
||||
|
||||
try_again:
|
||||
last_finalized_seq = desc_last_finalized_seq(rb);
|
||||
|
||||
/*
|
||||
* @head_id is loaded after @last_finalized_seq to ensure that
|
||||
* it points to the record with @last_finalized_seq or newer.
|
||||
*
|
||||
* Memory barrier involvement:
|
||||
*
|
||||
* If desc_last_finalized_seq:A reads from
|
||||
* desc_update_last_finalized:A, then
|
||||
* prb_next_reserve_seq:A reads from desc_reserve:D.
|
||||
*
|
||||
* Relies on:
|
||||
*
|
||||
* RELEASE from desc_reserve:D to desc_update_last_finalized:A
|
||||
* matching
|
||||
* ACQUIRE from desc_last_finalized_seq:A to prb_next_reserve_seq:A
|
||||
*
|
||||
* Note: desc_reserve:D and desc_update_last_finalized:A can be
|
||||
* different CPUs. However, the desc_update_last_finalized:A CPU
|
||||
* (which performs the release) must have previously seen
|
||||
* desc_read:C, which implies desc_reserve:D can be seen.
|
||||
*/
|
||||
head_id = atomic_long_read(&desc_ring->head_id); /* LMM(prb_next_reserve_seq:A) */
|
||||
|
||||
d = to_desc(desc_ring, last_finalized_seq);
|
||||
state_var = &d->state_var;
|
||||
|
||||
/* Extract the ID, used to specify the descriptor to read. */
|
||||
last_finalized_id = DESC_ID(atomic_long_read(state_var));
|
||||
|
||||
/* Ensure @last_finalized_id is correct. */
|
||||
err = desc_read_finalized_seq(desc_ring, last_finalized_id, last_finalized_seq, &desc);
|
||||
|
||||
if (err == -EINVAL) {
|
||||
if (last_finalized_seq == 0) {
|
||||
/*
|
||||
* No record has been finalized or even reserved yet.
|
||||
*
|
||||
* The @head_id is initialized such that the first
|
||||
* increment will yield the first record (seq=0).
|
||||
* Handle it separately to avoid a negative @diff
|
||||
* below.
|
||||
*/
|
||||
if (head_id == DESC0_ID(desc_ring->count_bits))
|
||||
return 0;
|
||||
|
||||
/*
|
||||
* One or more descriptors are already reserved. Use
|
||||
* the descriptor ID of the first one (@seq=0) for
|
||||
* the @diff below.
|
||||
*/
|
||||
last_finalized_id = DESC0_ID(desc_ring->count_bits) + 1;
|
||||
} else {
|
||||
/* Record must have been overwritten. Try again. */
|
||||
goto try_again;
|
||||
}
|
||||
}
|
||||
|
||||
/* Diff of known descriptor IDs to compute related sequence numbers. */
|
||||
diff = head_id - last_finalized_id;
|
||||
|
||||
/*
|
||||
* @head_id points to the most recently reserved record, but this
|
||||
* function returns the sequence number that will be assigned to the
|
||||
* next (not yet reserved) record. Thus +1 is needed.
|
||||
*/
|
||||
return (last_finalized_seq + diff + 1);
|
||||
}
|
||||
|
||||
/*
|
||||
* Non-blocking read of a record.
|
||||
*
|
||||
* On success @seq is updated to the record that was read and (if provided)
|
||||
* @r and @line_count will contain the read/calculated data.
|
||||
*
|
||||
* On failure @seq is updated to a record that is not yet available to the
|
||||
* reader, but it will be the next record available to the reader.
|
||||
*
|
||||
* Note: When the current CPU is in panic, this function will skip over any
|
||||
* non-existent/non-finalized records in order to allow the panic CPU
|
||||
* to print any and all records that have been finalized.
|
||||
*/
|
||||
static bool _prb_read_valid(struct printk_ringbuffer *rb, u64 *seq,
|
||||
struct printk_record *r, unsigned int *line_count)
|
||||
|
|
@ -1899,12 +2121,32 @@ static bool _prb_read_valid(struct printk_ringbuffer *rb, u64 *seq,
|
|||
*seq = tail_seq;
|
||||
|
||||
} else if (err == -ENOENT) {
|
||||
/* Record exists, but no data available. Skip. */
|
||||
/* Record exists, but the data was lost. Skip. */
|
||||
(*seq)++;
|
||||
|
||||
} else {
|
||||
/* Non-existent/non-finalized record. Must stop. */
|
||||
return false;
|
||||
/*
|
||||
* Non-existent/non-finalized record. Must stop.
|
||||
*
|
||||
* For panic situations it cannot be expected that
|
||||
* non-finalized records will become finalized. But
|
||||
* there may be other finalized records beyond that
|
||||
* need to be printed for a panic situation. If this
|
||||
* is the panic CPU, skip this
|
||||
* non-existent/non-finalized record unless it is
|
||||
* at or beyond the head, in which case it is not
|
||||
* possible to continue.
|
||||
*
|
||||
* Note that new messages printed on panic CPU are
|
||||
* finalized when we are here. The only exception
|
||||
* might be the last message without trailing newline.
|
||||
* But it would have the sequence number returned
|
||||
* by "prb_next_reserve_seq() - 1".
|
||||
*/
|
||||
if (this_cpu_in_panic() && ((*seq + 1) < prb_next_reserve_seq(rb)))
|
||||
(*seq)++;
|
||||
else
|
||||
return false;
|
||||
}
|
||||
}
|
||||
|
||||
|
|
@ -1932,7 +2174,7 @@ static bool _prb_read_valid(struct printk_ringbuffer *rb, u64 *seq,
|
|||
* On success, the reader must check r->info.seq to see which record was
|
||||
* actually read. This allows the reader to detect dropped records.
|
||||
*
|
||||
* Failure means @seq refers to a not yet written record.
|
||||
* Failure means @seq refers to a record not yet available to the reader.
|
||||
*/
|
||||
bool prb_read_valid(struct printk_ringbuffer *rb, u64 seq,
|
||||
struct printk_record *r)
|
||||
|
|
@ -1962,7 +2204,7 @@ bool prb_read_valid(struct printk_ringbuffer *rb, u64 seq,
|
|||
* On success, the reader must check info->seq to see which record meta data
|
||||
* was actually read. This allows the reader to detect dropped records.
|
||||
*
|
||||
* Failure means @seq refers to a not yet written record.
|
||||
* Failure means @seq refers to a record not yet available to the reader.
|
||||
*/
|
||||
bool prb_read_valid_info(struct printk_ringbuffer *rb, u64 seq,
|
||||
struct printk_info *info, unsigned int *line_count)
|
||||
|
|
@ -2008,7 +2250,9 @@ u64 prb_first_valid_seq(struct printk_ringbuffer *rb)
|
|||
* newest sequence number available to readers will be.
|
||||
*
|
||||
* This provides readers a sequence number to jump to if all currently
|
||||
* available records should be skipped.
|
||||
* available records should be skipped. It is guaranteed that all records
|
||||
* previous to the returned value have been finalized and are (or were)
|
||||
* available to the reader.
|
||||
*
|
||||
* Context: Any context.
|
||||
* Return: The sequence number of the next newest (not yet available) record
|
||||
|
|
@ -2016,34 +2260,19 @@ u64 prb_first_valid_seq(struct printk_ringbuffer *rb)
|
|||
*/
|
||||
u64 prb_next_seq(struct printk_ringbuffer *rb)
|
||||
{
|
||||
struct prb_desc_ring *desc_ring = &rb->desc_ring;
|
||||
enum desc_state d_state;
|
||||
unsigned long id;
|
||||
u64 seq;
|
||||
|
||||
/* Check if the cached @id still points to a valid @seq. */
|
||||
id = atomic_long_read(&desc_ring->last_finalized_id);
|
||||
d_state = desc_read(desc_ring, id, NULL, &seq, NULL);
|
||||
seq = desc_last_finalized_seq(rb);
|
||||
|
||||
if (d_state == desc_finalized || d_state == desc_reusable) {
|
||||
/*
|
||||
* Begin searching after the last finalized record.
|
||||
*
|
||||
* On 0, the search must begin at 0 because of hack#2
|
||||
* of the bootstrapping phase it is not known if a
|
||||
* record at index 0 exists.
|
||||
*/
|
||||
if (seq != 0)
|
||||
seq++;
|
||||
} else {
|
||||
/*
|
||||
* The information about the last finalized sequence number
|
||||
* has gone. It should happen only when there is a flood of
|
||||
* new messages and the ringbuffer is rapidly recycled.
|
||||
* Give up and start from the beginning.
|
||||
*/
|
||||
seq = 0;
|
||||
}
|
||||
/*
|
||||
* Begin searching after the last finalized record.
|
||||
*
|
||||
* On 0, the search must begin at 0 because of hack#2
|
||||
* of the bootstrapping phase it is not known if a
|
||||
* record at index 0 exists.
|
||||
*/
|
||||
if (seq != 0)
|
||||
seq++;
|
||||
|
||||
/*
|
||||
* The information about the last finalized @seq might be inaccurate.
|
||||
|
|
@ -2085,7 +2314,7 @@ void prb_init(struct printk_ringbuffer *rb,
|
|||
rb->desc_ring.infos = infos;
|
||||
atomic_long_set(&rb->desc_ring.head_id, DESC0_ID(descbits));
|
||||
atomic_long_set(&rb->desc_ring.tail_id, DESC0_ID(descbits));
|
||||
atomic_long_set(&rb->desc_ring.last_finalized_id, DESC0_ID(descbits));
|
||||
atomic_long_set(&rb->desc_ring.last_finalized_seq, 0);
|
||||
|
||||
rb->text_data_ring.size_bits = textbits;
|
||||
rb->text_data_ring.data = text_buf;
|
||||
|
|
|
|||
|
|
@ -75,7 +75,7 @@ struct prb_desc_ring {
|
|||
struct printk_info *infos;
|
||||
atomic_long_t head_id;
|
||||
atomic_long_t tail_id;
|
||||
atomic_long_t last_finalized_id;
|
||||
atomic_long_t last_finalized_seq;
|
||||
};
|
||||
|
||||
/*
|
||||
|
|
@ -127,8 +127,22 @@ enum desc_state {
|
|||
#define DESC_SV(id, state) (((unsigned long)state << DESC_FLAGS_SHIFT) | id)
|
||||
#define DESC_ID_MASK (~DESC_FLAGS_MASK)
|
||||
#define DESC_ID(sv) ((sv) & DESC_ID_MASK)
|
||||
|
||||
/*
|
||||
* Special data block logical position values (for fields of
|
||||
* @prb_desc.text_blk_lpos).
|
||||
*
|
||||
* - Bit0 is used to identify if the record has no data block. (Implemented in
|
||||
* the LPOS_DATALESS() macro.)
|
||||
*
|
||||
* - Bit1 specifies the reason for not having a data block.
|
||||
*
|
||||
* These special values could never be real lpos values because of the
|
||||
* meta data and alignment padding of data blocks. (See to_blk_size() for
|
||||
* details.)
|
||||
*/
|
||||
#define FAILED_LPOS 0x1
|
||||
#define NO_LPOS 0x3
|
||||
#define EMPTY_LINE_LPOS 0x3
|
||||
|
||||
#define FAILED_BLK_LPOS \
|
||||
{ \
|
||||
|
|
@ -259,7 +273,7 @@ static struct printk_ringbuffer name = { \
|
|||
.infos = &_##name##_infos[0], \
|
||||
.head_id = ATOMIC_INIT(DESC0_ID(descbits)), \
|
||||
.tail_id = ATOMIC_INIT(DESC0_ID(descbits)), \
|
||||
.last_finalized_id = ATOMIC_INIT(DESC0_ID(descbits)), \
|
||||
.last_finalized_seq = ATOMIC_INIT(0), \
|
||||
}, \
|
||||
.text_data_ring = { \
|
||||
.size_bits = (avgtextbits) + (descbits), \
|
||||
|
|
@ -378,7 +392,41 @@ bool prb_read_valid(struct printk_ringbuffer *rb, u64 seq,
|
|||
bool prb_read_valid_info(struct printk_ringbuffer *rb, u64 seq,
|
||||
struct printk_info *info, unsigned int *line_count);
|
||||
|
||||
u64 prb_first_seq(struct printk_ringbuffer *rb);
|
||||
u64 prb_first_valid_seq(struct printk_ringbuffer *rb);
|
||||
u64 prb_next_seq(struct printk_ringbuffer *rb);
|
||||
u64 prb_next_reserve_seq(struct printk_ringbuffer *rb);
|
||||
|
||||
#ifdef CONFIG_64BIT
|
||||
|
||||
#define __u64seq_to_ulseq(u64seq) (u64seq)
|
||||
#define __ulseq_to_u64seq(rb, ulseq) (ulseq)
|
||||
|
||||
#else /* CONFIG_64BIT */
|
||||
|
||||
#define __u64seq_to_ulseq(u64seq) ((u32)u64seq)
|
||||
|
||||
static inline u64 __ulseq_to_u64seq(struct printk_ringbuffer *rb, u32 ulseq)
|
||||
{
|
||||
u64 rb_first_seq = prb_first_seq(rb);
|
||||
u64 seq;
|
||||
|
||||
/*
|
||||
* The provided sequence is only the lower 32 bits of the ringbuffer
|
||||
* sequence. It needs to be expanded to 64bit. Get the first sequence
|
||||
* number from the ringbuffer and fold it.
|
||||
*
|
||||
* Having a 32bit representation in the console is sufficient.
|
||||
* If a console ever gets more than 2^31 records behind
|
||||
* the ringbuffer then this is the least of the problems.
|
||||
*
|
||||
* Also the access to the ring buffer is always safe.
|
||||
*/
|
||||
seq = rb_first_seq - (s32)((u32)rb_first_seq - ulseq);
|
||||
|
||||
return seq;
|
||||
}
|
||||
|
||||
#endif /* CONFIG_64BIT */
|
||||
|
||||
#endif /* _KERNEL_PRINTK_RINGBUFFER_H */
|
||||
|
|
|
|||
|
|
@ -96,15 +96,25 @@ static void __dump_stack(const char *log_lvl)
|
|||
*/
|
||||
asmlinkage __visible void dump_stack_lvl(const char *log_lvl)
|
||||
{
|
||||
bool in_panic = this_cpu_in_panic();
|
||||
unsigned long flags;
|
||||
|
||||
/*
|
||||
* Permit this cpu to perform nested stack dumps while serialising
|
||||
* against other CPUs
|
||||
* against other CPUs, unless this CPU is in panic.
|
||||
*
|
||||
* When in panic, non-panic CPUs are not permitted to store new
|
||||
* printk messages so there is no need to synchronize the output.
|
||||
* This avoids potential deadlock in panic() if another CPU is
|
||||
* holding and unable to release the printk_cpu_sync.
|
||||
*/
|
||||
printk_cpu_sync_get_irqsave(flags);
|
||||
if (!in_panic)
|
||||
printk_cpu_sync_get_irqsave(flags);
|
||||
|
||||
__dump_stack(log_lvl);
|
||||
printk_cpu_sync_put_irqrestore(flags);
|
||||
|
||||
if (!in_panic)
|
||||
printk_cpu_sync_put_irqrestore(flags);
|
||||
}
|
||||
EXPORT_SYMBOL(dump_stack_lvl);
|
||||
|
||||
|
|
|
|||
Loading…
Reference in New Issue