s390/sclp_vt220: support magic sysrequests
authorHendrik Brueckner <brueckner@linux.vnet.ibm.com>
Mon, 17 Aug 2015 14:13:41 +0000 (16:13 +0200)
committerMartin Schwidefsky <schwidefsky@de.ibm.com>
Wed, 26 Aug 2015 15:20:45 +0000 (17:20 +0200)
commit1d3f9094c6fdb5680fd3b19a5b153308d53a70ee
treea3d5dfab22fde888559db8c872c4739db14b9752
parentab7373bf235ede864a72f0d2f8f9a21a1748c4a2
s390/sclp_vt220: support magic sysrequests

Implement magic sysrequest handling for the VT220 terminal (also known as
the Integrated ASCII console on the HMC/SE).
To invoke a "magic sysrequest" function, press "Ctrl+o" followed by a
second character that designates the debugging function.

The handling of the sysrq is scheduled away from the SCLP IRQ context;
because large amounts of sysrq output might fill up the console buffers.
The console might deadlock because it cannot empty the buffers while still
in the receiving IRQ context.  This behavior is the same as for the SCLP
console.

Reported-by: Horst Weber <hweber@de.ibm.com>
Signed-off-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Reviewed-by: Peter Oberparleiter <oberpar@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
drivers/s390/char/sclp_vt220.c