diff options
| author | Sebastian Andrzej Siewior <bigeasy@linutronix.de> | 2013-03-21 19:01:05 +0100 |
|---|---|---|
| committer | Andrey Konovalov <andrey.konovalov@linaro.org> | 2013-06-14 18:38:04 +0400 |
| commit | c1f78a9b0f558cd58140ceccc757e44d12dde2a5 (patch) | |
| tree | 9d28f142d7ad82ee08ef7007b5f13a8cefd1164d | |
| parent | bfe5659514abf317259b7b2afc0499f8b9c0199d (diff) | |
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>
| -rw-r--r-- | kernel/printk.c | 27 |
1 files changed, 26 insertions, 1 deletions
diff --git a/kernel/printk.c b/kernel/printk.c index 2609082e3ca8..6d52c343ed8e 100644 --- a/kernel/printk.c +++ b/kernel/printk.c @@ -1072,6 +1072,7 @@ 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) @@ -1083,7 +1084,14 @@ 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; @@ -1104,6 +1112,14 @@ 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 */ @@ -1117,6 +1133,14 @@ 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 */ @@ -1158,6 +1182,7 @@ 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); |