@@ -161,6 +161,8 @@ Command Function
will be printed to your console. (``0``, for example would make
it so that only emergency messages like PANICs or OOPSes would
make it to your console.)
+
+``,`` Wait for one second (only for use with /proc/sysrq-trigger batch)
=========== ===================================================================
Okay, so what can I use them for?
@@ -51,6 +51,7 @@
#include <linux/syscalls.h>
#include <linux/of.h>
#include <linux/rcupdate.h>
+#include <linux/delay.h>
#include <asm/ptrace.h>
#include <asm/irq_regs.h>
@@ -1166,10 +1167,21 @@ static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf,
if (get_user(c, buf + i))
return -EFAULT;
- if (c == '_')
+ switch (c) {
+
+ case '_':
bulk = true;
- else
+ break;
+
+ case ',':
+ msleep(1000);
+ break;
+
+ default:
__handle_sysrq(c, false);
+ break;
+
+ }
if (!bulk)
break;
Writing ',' to /proc/sysrq-trigger now causes processing to pause for one second. This is useful, because recently accepted patch allows to write multiple keys at once to /proc/sysrq-trigger. But it might be desirable to add slight delay between actions. Eg. between (e)TERM and (i)KILL it makes sense to put slight delay, so processes have chance to run TERM handlers before being KILLed. Now we can send TERM, wait for two seconds and KILL like this: echo _e,,i > /proc/sysrq-trigger Originaly i've tested doing this as handler registered in sysrq_key_table[], but that would cause delay to occur while holding sysrq rcu lock in __handle_sysrq(), therefore i've decided to implement this in write_sysrq_trigger() instead to allow proper use of msleep() instead of mdelay() in locked context. This means it will only be possible to invoke the delay using /proc/sysrq-trigger, but there is little point in doing that interactively using keyboard anyway. Depends-on: /proc/sysrq-trigger: accept multiple keys at once Signed-off-by: Tomas Mudrunka <tomas.mudrunka@gmail.com> --- Documentation/admin-guide/sysrq.rst | 2 ++ drivers/tty/sysrq.c | 16 ++++++++++++++-- 2 files changed, 16 insertions(+), 2 deletions(-)