diff options
| author | Sebastian Andrzej Siewior <bigeasy@linutronix.de> | 2013-03-21 19:01:05 +0100 |
|---|---|---|
| committer | Sebastian Andrzej Siewior <bigeasy@linutronix.de> | 2016-02-13 00:36:24 +0100 |
| commit | 721bd57695ee6d0d523c857194912ad477e5fa57 (patch) | |
| tree | c36c2213c8e3d698f4ce7750c316fe88356e6f2e | |
| parent | 8b243b07a24ba4fbfa77d301efc5fad6f0dae3fa (diff) | |
| download | rt-linux-721bd57695ee6d0d523c857194912ad477e5fa57.tar.gz | |
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/printk.c | 27 |
1 files changed, 26 insertions, 1 deletions
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 763af49002fc08..88995de2ee5347 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -1262,6 +1262,7 @@ 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) @@ -1273,7 +1274,14 @@ 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; @@ -1294,6 +1302,14 @@ 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 */ @@ -1307,6 +1323,14 @@ 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 */ @@ -1347,6 +1371,7 @@ 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); |