diff options
| author | Sebastian Andrzej Siewior <bigeasy@linutronix.de> | 2013-03-21 18:01:05 (GMT) |
|---|---|---|
| committer | Scott Wood <scottwood@freescale.com> | 2014-05-14 18:38:41 (GMT) |
| commit | 632930123b22e3a64946bec93b9880bd649fe23a (patch) | |
| tree | 4f972f634ebfe37a240183b11fb4955bc62ed1d2 /kernel | |
| parent | 4ccae68638780917daf37a0941bf3280d17ef8b4 (diff) | |
| download | linux-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.c | 27 |
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); |