diff options
Diffstat (limited to '')
| -rw-r--r-- | debian/patches-rt/0208-printk-Drop-the-logbuf_lock-more-often.patch | 83 |
1 files changed, 83 insertions, 0 deletions
diff --git a/debian/patches-rt/0208-printk-Drop-the-logbuf_lock-more-often.patch b/debian/patches-rt/0208-printk-Drop-the-logbuf_lock-more-often.patch new file mode 100644 index 000000000..bc4f44f50 --- /dev/null +++ b/debian/patches-rt/0208-printk-Drop-the-logbuf_lock-more-often.patch @@ -0,0 +1,83 @@ +From b4bf7654e00cd7da0d18577698e25eb199de2d57 Mon Sep 17 00:00:00 2001 +From: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +Date: Thu, 21 Mar 2013 19:01:05 +0100 +Subject: [PATCH 208/347] printk: Drop the logbuf_lock more often +Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patches-4.19.246-rt110.tar.xz + +The lock is hold with irgs off. The latency drops 500us+ on my arm bugs +with a "full" buffer after executing "dmesg" on the shell. + +Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +--- + kernel/printk/printk.c | 28 ++++++++++++++++++++++++++++ + 1 file changed, 28 insertions(+) + +diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c +index 273f2c7864b5..1e0988a0bb97 100644 +--- a/kernel/printk/printk.c ++++ b/kernel/printk/printk.c +@@ -1457,12 +1457,23 @@ static int syslog_print_all(char __user *buf, int size, bool clear) + u64 next_seq; + u64 seq; + u32 idx; ++ int attempts = 0; ++ int num_msg; + + text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL); + if (!text) + return -ENOMEM; + + logbuf_lock_irq(); ++ ++try_again: ++ attempts++; ++ if (attempts > 10) { ++ len = -EBUSY; ++ goto out; ++ } ++ num_msg = 0; ++ + /* + * Find first record that fits, including all following records, + * into the user-provided buffer for this dump. +@@ -1475,6 +1486,14 @@ static int syslog_print_all(char __user *buf, int size, bool clear) + len += msg_print_text(msg, true, NULL, 0); + idx = log_next(idx); + seq++; ++ num_msg++; ++ if (num_msg > 5) { ++ num_msg = 0; ++ logbuf_unlock_irq(); ++ logbuf_lock_irq(); ++ if (clear_seq < log_first_seq) ++ goto try_again; ++ } + } + + /* move first record forward until length fits into the buffer */ +@@ -1486,6 +1505,14 @@ static int syslog_print_all(char __user *buf, int size, bool clear) + len -= msg_print_text(msg, true, NULL, 0); + idx = log_next(idx); + seq++; ++ num_msg++; ++ if (num_msg > 5) { ++ num_msg = 0; ++ logbuf_unlock_irq(); ++ logbuf_lock_irq(); ++ if (clear_seq < log_first_seq) ++ goto try_again; ++ } + } + + /* last message fitting into this dump */ +@@ -1523,6 +1550,7 @@ static int syslog_print_all(char __user *buf, int size, bool clear) + clear_seq = log_next_seq; + clear_idx = log_next_idx; + } ++out: + logbuf_unlock_irq(); + + kfree(text); +-- +2.36.1 + |