diff options
Diffstat (limited to 'features/rt/printk-add-syslog_lock.patch')
| -rw-r--r-- | features/rt/printk-add-syslog_lock.patch | 158 |
1 files changed, 158 insertions, 0 deletions
diff --git a/features/rt/printk-add-syslog_lock.patch b/features/rt/printk-add-syslog_lock.patch new file mode 100644 index 00000000..741d96e2 --- /dev/null +++ b/features/rt/printk-add-syslog_lock.patch @@ -0,0 +1,158 @@ +From 2b8baa6554441c2caba94ff88245cf653796b8cf Mon Sep 17 00:00:00 2001 +From: John Ogness <john.ogness@linutronix.de> +Date: Thu, 10 Dec 2020 16:58:02 +0106 +Subject: [PATCH 014/191] printk: add syslog_lock + +The global variables @syslog_seq, @syslog_partial, @syslog_time +and write access to @clear_seq are protected by @logbuf_lock. +Once @logbuf_lock is removed, these variables will need their +own synchronization method. Introduce @syslog_lock for this +purpose. + +@syslog_lock is a raw_spin_lock for now. This simplifies the +transition to removing @logbuf_lock. Once @logbuf_lock and the +safe buffers are removed, @syslog_lock can change to spin_lock. + +Signed-off-by: John Ogness <john.ogness@linutronix.de> +Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +--- + kernel/printk/printk.c | 41 +++++++++++++++++++++++++++++++++++++---- + 1 file changed, 37 insertions(+), 4 deletions(-) + +diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c +index 0031bb2156d1..713d09843d23 100644 +--- a/kernel/printk/printk.c ++++ b/kernel/printk/printk.c +@@ -390,8 +390,12 @@ DEFINE_RAW_SPINLOCK(logbuf_lock); + printk_safe_exit_irqrestore(flags); \ + } while (0) + ++/* syslog_lock protects syslog_* variables and write access to clear_seq. */ ++static DEFINE_RAW_SPINLOCK(syslog_lock); ++ + #ifdef CONFIG_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 */ + static u64 syslog_seq; + static size_t syslog_partial; +@@ -410,7 +414,7 @@ struct latched_seq { + /* + * The next printk record to read after the last 'clear' command. There are + * two copies (updated with seqcount_latch) so that reads can locklessly +- * access a valid value. Writers are synchronized by @logbuf_lock. ++ * access a valid value. Writers are synchronized by @syslog_lock. + */ + static struct latched_seq clear_seq = { + .latch = SEQCNT_LATCH_ZERO(clear_seq.latch), +@@ -470,7 +474,7 @@ bool printk_percpu_data_ready(void) + return __printk_percpu_data_ready; + } + +-/* Must be called under logbuf_lock. */ ++/* Must be called under syslog_lock. */ + static void latched_seq_write(struct latched_seq *ls, u64 val) + { + raw_write_seqcount_latch(&ls->latch); +@@ -1529,7 +1533,9 @@ static int syslog_print(char __user *buf, int size) + size_t skip; + + logbuf_lock_irq(); ++ raw_spin_lock(&syslog_lock); + if (!prb_read_valid(prb, syslog_seq, &r)) { ++ raw_spin_unlock(&syslog_lock); + logbuf_unlock_irq(); + break; + } +@@ -1559,6 +1565,7 @@ static int syslog_print(char __user *buf, int size) + syslog_partial += n; + } else + n = 0; ++ raw_spin_unlock(&syslog_lock); + logbuf_unlock_irq(); + + if (!n) +@@ -1625,8 +1632,11 @@ static int syslog_print_all(char __user *buf, int size, bool clear) + break; + } + +- if (clear) ++ if (clear) { ++ raw_spin_lock(&syslog_lock); + latched_seq_write(&clear_seq, seq); ++ raw_spin_unlock(&syslog_lock); ++ } + logbuf_unlock_irq(); + + kfree(text); +@@ -1636,10 +1646,24 @@ static int syslog_print_all(char __user *buf, int size, bool clear) + static void syslog_clear(void) + { + logbuf_lock_irq(); ++ raw_spin_lock(&syslog_lock); + latched_seq_write(&clear_seq, prb_next_seq(prb)); ++ raw_spin_unlock(&syslog_lock); + logbuf_unlock_irq(); + } + ++/* Return a consistent copy of @syslog_seq. */ ++static u64 read_syslog_seq_irq(void) ++{ ++ u64 seq; ++ ++ raw_spin_lock_irq(&syslog_lock); ++ seq = syslog_seq; ++ raw_spin_unlock_irq(&syslog_lock); ++ ++ return seq; ++} ++ + int do_syslog(int type, char __user *buf, int len, int source) + { + struct printk_info info; +@@ -1663,8 +1687,9 @@ int do_syslog(int type, char __user *buf, int len, int source) + return 0; + if (!access_ok(buf, len)) + return -EFAULT; ++ + error = wait_event_interruptible(log_wait, +- prb_read_valid(prb, syslog_seq, NULL)); ++ prb_read_valid(prb, read_syslog_seq_irq(), NULL)); + if (error) + return error; + error = syslog_print(buf, len); +@@ -1713,8 +1738,10 @@ 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(); ++ raw_spin_lock(&syslog_lock); + if (!prb_read_valid_info(prb, syslog_seq, &info, NULL)) { + /* No unread messages. */ ++ raw_spin_unlock(&syslog_lock); + logbuf_unlock_irq(); + return 0; + } +@@ -1743,6 +1770,7 @@ int do_syslog(int type, char __user *buf, int len, int source) + } + error -= syslog_partial; + } ++ raw_spin_unlock(&syslog_lock); + logbuf_unlock_irq(); + break; + /* Size of the log buffer */ +@@ -2992,7 +3020,12 @@ void register_console(struct console *newcon) + */ + exclusive_console = newcon; + exclusive_console_stop_seq = console_seq; ++ ++ /* Get a consistent copy of @syslog_seq. */ ++ raw_spin_lock(&syslog_lock); + console_seq = syslog_seq; ++ raw_spin_unlock(&syslog_lock); ++ + logbuf_unlock_irqrestore(flags); + } + console_unlock(); +-- +2.19.1 + |