linux-toradex.git/kernel/printk.c, branch v3.2.9-rt16

sysrq: Allow immediate Magic SysRq output for PREEMPT_RT_FULL

2012-03-06T16:18:02+00:00

Add a CONFIG option to allow the output from Magic SysRq to be output
immediately, even if this causes large latencies.

If PREEMPT_RT_FULL, printk() will not try to acquire the console lock
when interrupts or preemption are disabled.  If the console lock is
not acquired the printk() output will be buffered, but will not be
output immediately. Some drivers call into the Magic SysRq code
with interrupts or preemption disabled, so the output of Magic SysRq
will be buffered instead of printing immediately if this option is
not selected.

Even with this option selected, Magic SysRq output will be delayed
if the attempt to acquire the console lock fails.

Signed-off-by: Frank Rowand 
Link: http://lkml.kernel.org/r/4E7CEF60.5020508@am.sony.com
Signed-off-by: Thomas Gleixner

printk: Disable migration instead of preemption

2012-03-06T16:18:00+00:00

There is no need do disable preemption in vprintk(), disable_migrate()
is sufficient. This fixes the following bug in -rt:

[   14.759233] BUG: sleeping function called from invalid context
at /home/rw/linux-rt/kernel/rtmutex.c:645
[   14.759235] in_atomic(): 1, irqs_disabled(): 0, pid: 547, name: bash
[   14.759244] Pid: 547, comm: bash Not tainted 3.0.12-rt29+ #3
[   14.759246] Call Trace:
[   14.759301]  [] __might_sleep+0xeb/0xf0
[   14.759318]  [] rt_spin_lock_fastlock.constprop.9+0x21/0x43
[   14.759336]  [] rt_spin_lock+0xe/0x10
[   14.759354]  [] serial8250_console_write+0x81/0x121
[   14.759366]  [] __call_console_drivers+0x7c/0x93
[   14.759369]  [] _call_console_drivers+0x5c/0x60
[   14.759372]  [] console_unlock+0x147/0x1a2
[   14.759374]  [] vprintk+0x3ea/0x462
[   14.759383]  [] printk+0x51/0x53
[   14.759399]  [] ? proc_reg_poll+0x9a/0x9a
[   14.759403]  [] __handle_sysrq+0x50/0x14d
[   14.759406]  [] write_sysrq_trigger+0x4b/0x53
[   14.759408]  [] ? __handle_sysrq+0x14d/0x14d
[   14.759410]  [] proc_reg_write+0x9f/0xbe
[   14.759426]  [] vfs_write+0xac/0xf3
[   14.759429]  [] ? fget_light+0x3a/0x9b
[   14.759431]  [] sys_write+0x4a/0x6e
[   14.759438]  [] system_call_fastpath+0x16/0x1b

Signed-off-by: Richard Weinberger 
Link: http://lkml.kernel.org/r/1323696956-11445-1-git-send-email-rw@linutronix.de
Signed-off-by: Thomas Gleixner

console-make-rt-friendly.patch

2012-03-06T16:18:00+00:00

Signed-off-by: Thomas Gleixner

printk: Don't call printk_tick in printk_needs_cpu() on RT

2012-03-06T16:17:46+00:00

printk_tick() can't be called in atomic context when RT is enabled,
otherwise below warning will show:

[  117.597095] BUG: sleeping function called from invalid context at kernel/rtmutex.c:645
[  117.597102] in_atomic(): 1, irqs_disabled(): 1, pid: 0, name: kworker/0:0
[  117.597111] Pid: 0, comm: kworker/0:0 Not tainted 3.0.6-rt17-00284-gb76d419-dirty #7
[  117.597116] Call Trace:
[  117.597131]  [] ? printk+0x1d/0x24
[  117.597142]  [] __might_sleep+0xe6/0x110
[  117.597151]  [] rt_spin_lock+0x1c/0x30
[  117.597158]  [] __wake_up+0x26/0x60
[  117.597166]  [] printk_tick+0x3e/0x40
[  117.597173]  [] printk_needs_cpu+0x24/0x30
[  117.597181]  [] tick_nohz_stop_sched_tick+0x2e8/0x410
[  117.597191]  [] ? sched_clock_idle_wakeup_event+0x1a/0x20
[  117.597201]  [] cpu_idle+0x4a/0xb0
[  117.597209]  [] start_secondary+0xd3/0xd7

Now this is a really rare case and it's very unlikely that we starve
an logbuf waiter that way.

Signed-off-by: Yong Zhang 
Link: http://lkml.kernel.org/r/1318762607-2261-4-git-send-email-yong.zhang0@gmail.com
Signed-off-by: Thomas Gleixner

printk: 'force_early_printk' boot param to help with debugging

2012-03-06T16:17:37+00:00

Gives me an option to screw printk and actually see what the machine
says.

Signed-off-by: Peter Zijlstra 
Link: http://lkml.kernel.org/r/1314967289.1301.11.camel@twins
Signed-off-by: Thomas Gleixner 
Link: http://lkml.kernel.org/n/tip-ykb97nsfmobq44xketrxs977@git.kernel.org

printk-kill.patch

2012-03-06T16:17:37+00:00

Signed-off-by: Thomas Gleixner

early-printk-consolidate.patch

2012-03-06T16:17:37+00:00

Signed-off-by: Thomas Gleixner

printk: avoid double lock acquire

2011-12-09T15:50:28+00:00

Commit 4f2a8d3cf5e ("printk: Fix console_sem vs logbuf_lock unlock race")
introduced another silly bug where we would want to acquire an already
held lock.  Avoid this.

Reported-by: Andrea Arcangeli 
Signed-off-by: Peter Zijlstra 
Cc: Ingo Molnar 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

printk: remove bounds checking for log_prefix

2011-11-01T00:30:53+00:00

Currently log_prefix is testing that the first character of the log level
and facility is less than '0' and greater than '9' (which is always
false).

Since the code being updated works because strtoul bombs out (endp isn't
updated) and 0 is returned anyway just remove the check and don't change
the behavior of the function.

Signed-off-by: William Douglas 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

printk: fix bounds checking for log_prefix

2011-11-01T00:30:53+00:00

Currently log_prefix is testing that the first character of the log level
and facility is less than '0' and greater than '9' (which is always
false).  It should be testing to see if the character less than '0' or
greater than '9' instead.  This patch makes that change.

The code being changed worked because strtoul bombs out (endp isn't
updated) and 0 is returned anyway.

Signed-off-by: William Douglas 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds