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authorSebastian Andrzej Siewior <bigeasy@linutronix.de>2013-03-21 18:01:05 (GMT)
committerScott Wood <scottwood@freescale.com>2014-05-14 18:38:41 (GMT)
commit632930123b22e3a64946bec93b9880bd649fe23a (patch)
tree4f972f634ebfe37a240183b11fb4955bc62ed1d2 /kernel
parent4ccae68638780917daf37a0941bf3280d17ef8b4 (diff)
downloadlinux-fsl-qoriq-632930123b22e3a64946bec93b9880bd649fe23a.tar.xz
HACK: printk: drop the logbuf_lock more often
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>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/printk/printk.c27
1 files changed, 26 insertions, 1 deletions
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 4c68d20..981ff61 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -1029,6 +1029,7 @@ static int syslog_print_all(char __user *buf, int size, bool clear)
{
char *text;
int len = 0;
+ int attempts = 0;
text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
if (!text)
@@ -1040,7 +1041,14 @@ static int syslog_print_all(char __user *buf, int size, bool clear)
u64 seq;
u32 idx;
enum log_flags prev;
-
+ int num_msg;
+try_again:
+ attempts++;
+ if (attempts > 10) {
+ len = -EBUSY;
+ goto out;
+ }
+ num_msg = 0;
if (clear_seq < log_first_seq) {
/* messages are gone, move to first available one */
clear_seq = log_first_seq;
@@ -1061,6 +1069,14 @@ static int syslog_print_all(char __user *buf, int size, bool clear)
prev = msg->flags;
idx = log_next(idx);
seq++;
+ num_msg++;
+ if (num_msg > 5) {
+ num_msg = 0;
+ raw_spin_unlock_irq(&logbuf_lock);
+ raw_spin_lock_irq(&logbuf_lock);
+ if (clear_seq < log_first_seq)
+ goto try_again;
+ }
}
/* move first record forward until length fits into the buffer */
@@ -1074,6 +1090,14 @@ static int syslog_print_all(char __user *buf, int size, bool clear)
prev = msg->flags;
idx = log_next(idx);
seq++;
+ num_msg++;
+ if (num_msg > 5) {
+ num_msg = 0;
+ raw_spin_unlock_irq(&logbuf_lock);
+ raw_spin_lock_irq(&logbuf_lock);
+ if (clear_seq < log_first_seq)
+ goto try_again;
+ }
}
/* last message fitting into this dump */
@@ -1114,6 +1138,7 @@ static int syslog_print_all(char __user *buf, int size, bool clear)
clear_seq = log_next_seq;
clear_idx = log_next_idx;
}
+out:
raw_spin_unlock_irq(&logbuf_lock);
kfree(text);