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authorLinus Torvalds <torvalds@linux-foundation.org>2021-02-22 11:04:36 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2021-02-22 11:04:36 -0800
commitb2bec7d8a42a3885d525e821d9354b6b08fd6adf (patch)
tree8198d77e5b2fb8fc645ae42662b93a575910a032 /kernel
parent783955f03de770e94a1200b8f719975f8768e76c (diff)
parent16182ac1f02c8a5fc9753f9b8b5f3ef8c01707d8 (diff)
downloadlinux-b2bec7d8a42a3885d525e821d9354b6b08fd6adf.tar.gz
Merge tag 'printk-for-5.12' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux
Pull printk updates from Petr Mladek: - New "no_hash_pointers" kernel parameter causes that %p shows raw pointer values instead of hashed ones. It is intended only for debugging purposes. Misuse is prevented by a fat warning message that is inspired by trace_printk(). - Prevent a possible deadlock when flushing printk_safe buffers during panic(). - Fix performance regression caused by the lockless printk ringbuffer. It was visible with huge log buffer and long messages. - Documentation fix-up. * tag 'printk-for-5.12' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux: lib/vsprintf: no_hash_pointers prints all addresses as unhashed kselftest: add support for skipped tests lib: use KSTM_MODULE_GLOBALS macro in kselftest drivers printk: avoid prb_first_valid_seq() where possible printk: fix deadlock when kernel panic printk: rectify kernel-doc for prb_rec_init_wr()
Diffstat (limited to 'kernel')
-rw-r--r--kernel/printk/printk.c28
-rw-r--r--kernel/printk/printk_ringbuffer.h2
-rw-r--r--kernel/printk/printk_safe.c16
3 files changed, 31 insertions, 15 deletions
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 5a95c688621f..575a34b88936 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -735,9 +735,9 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf,
logbuf_lock_irq();
}
- if (user->seq < prb_first_valid_seq(prb)) {
+ if (r->info->seq != user->seq) {
/* our last seen message is gone, return error and reset */
- user->seq = prb_first_valid_seq(prb);
+ user->seq = r->info->seq;
ret = -EPIPE;
logbuf_unlock_irq();
goto out;
@@ -812,6 +812,7 @@ static loff_t devkmsg_llseek(struct file *file, loff_t offset, int whence)
static __poll_t devkmsg_poll(struct file *file, poll_table *wait)
{
struct devkmsg_user *user = file->private_data;
+ struct printk_info info;
__poll_t ret = 0;
if (!user)
@@ -820,9 +821,9 @@ static __poll_t devkmsg_poll(struct file *file, poll_table *wait)
poll_wait(file, &log_wait, wait);
logbuf_lock_irq();
- if (prb_read_valid(prb, user->seq, NULL)) {
+ if (prb_read_valid_info(prb, user->seq, &info, NULL)) {
/* return error when data has vanished underneath us */
- if (user->seq < prb_first_valid_seq(prb))
+ if (info.seq != user->seq)
ret = EPOLLIN|EPOLLRDNORM|EPOLLERR|EPOLLPRI;
else
ret = EPOLLIN|EPOLLRDNORM;
@@ -1559,6 +1560,7 @@ static void syslog_clear(void)
int do_syslog(int type, char __user *buf, int len, int source)
{
+ struct printk_info info;
bool clear = false;
static int saved_console_loglevel = LOGLEVEL_DEFAULT;
int error;
@@ -1629,9 +1631,14 @@ int do_syslog(int type, char __user *buf, int len, int source)
/* Number of chars in the log buffer */
case SYSLOG_ACTION_SIZE_UNREAD:
logbuf_lock_irq();
- if (syslog_seq < prb_first_valid_seq(prb)) {
+ if (!prb_read_valid_info(prb, syslog_seq, &info, NULL)) {
+ /* No unread messages. */
+ logbuf_unlock_irq();
+ return 0;
+ }
+ if (info.seq != syslog_seq) {
/* messages are gone, move to first one */
- syslog_seq = prb_first_valid_seq(prb);
+ syslog_seq = info.seq;
syslog_partial = 0;
}
if (source == SYSLOG_FROM_PROC) {
@@ -1643,7 +1650,6 @@ int do_syslog(int type, char __user *buf, int len, int source)
error = prb_next_seq(prb) - syslog_seq;
} else {
bool time = syslog_partial ? syslog_time : printk_time;
- struct printk_info info;
unsigned int line_count;
u64 seq;
@@ -3429,9 +3435,11 @@ bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
goto out;
logbuf_lock_irqsave(flags);
- if (dumper->cur_seq < prb_first_valid_seq(prb)) {
- /* messages are gone, move to first available one */
- dumper->cur_seq = prb_first_valid_seq(prb);
+ if (prb_read_valid_info(prb, dumper->cur_seq, &info, NULL)) {
+ if (info.seq != dumper->cur_seq) {
+ /* messages are gone, move to first available one */
+ dumper->cur_seq = info.seq;
+ }
}
/* last entry */
diff --git a/kernel/printk/printk_ringbuffer.h b/kernel/printk/printk_ringbuffer.h
index 5dc9d022db07..73cc80e01cef 100644
--- a/kernel/printk/printk_ringbuffer.h
+++ b/kernel/printk/printk_ringbuffer.h
@@ -287,7 +287,7 @@ _DEFINE_PRINTKRB(name, descbits, avgtextbits, &_##name##_text[0])
/* Writer Interface */
/**
- * prb_rec_init_wd() - Initialize a buffer for writing records.
+ * prb_rec_init_wr() - Initialize a buffer for writing records.
*
* @r: The record to initialize.
* @text_buf_size: The needed text buffer size.
diff --git a/kernel/printk/printk_safe.c b/kernel/printk/printk_safe.c
index a0e6f746de6c..2e9e3ed7d63e 100644
--- a/kernel/printk/printk_safe.c
+++ b/kernel/printk/printk_safe.c
@@ -45,6 +45,8 @@ struct printk_safe_seq_buf {
static DEFINE_PER_CPU(struct printk_safe_seq_buf, safe_print_seq);
static DEFINE_PER_CPU(int, printk_context);
+static DEFINE_RAW_SPINLOCK(safe_read_lock);
+
#ifdef CONFIG_PRINTK_NMI
static DEFINE_PER_CPU(struct printk_safe_seq_buf, nmi_print_seq);
#endif
@@ -180,8 +182,6 @@ static void report_message_lost(struct printk_safe_seq_buf *s)
*/
static void __printk_safe_flush(struct irq_work *work)
{
- static raw_spinlock_t read_lock =
- __RAW_SPIN_LOCK_INITIALIZER(read_lock);
struct printk_safe_seq_buf *s =
container_of(work, struct printk_safe_seq_buf, work);
unsigned long flags;
@@ -195,7 +195,7 @@ static void __printk_safe_flush(struct irq_work *work)
* different CPUs. This is especially important when printing
* a backtrace.
*/
- raw_spin_lock_irqsave(&read_lock, flags);
+ raw_spin_lock_irqsave(&safe_read_lock, flags);
i = 0;
more:
@@ -232,7 +232,7 @@ more:
out:
report_message_lost(s);
- raw_spin_unlock_irqrestore(&read_lock, flags);
+ raw_spin_unlock_irqrestore(&safe_read_lock, flags);
}
/**
@@ -278,6 +278,14 @@ void printk_safe_flush_on_panic(void)
raw_spin_lock_init(&logbuf_lock);
}
+ if (raw_spin_is_locked(&safe_read_lock)) {
+ if (num_online_cpus() > 1)
+ return;
+
+ debug_locks_off();
+ raw_spin_lock_init(&safe_read_lock);
+ }
+
printk_safe_flush();
}