Re: [Regression 2.6.35-rc1?] Sysrq works too well (no need of alt)

[Dmitry Torokhov <dmitry.torokhov@gmail.com>]

On Tue, Jun 08, 2010 at 05:37:42PM -0700, Dmitry Torokhov wrote:
> On Tuesday, June 08, 2010 03:55:08 pm Éric Piel wrote:
> > Op 08-06-10 11:33, Éric Piel schreef:
> > > Hello,
> > > I haven't investigated much yet, but I have the feeling that since
> > > 2.6.35-rc1 my "Print Screen/SysRq" key works only as SysRq: if I press
> > > it (normally assigned to take screenshot in gnome), nothing happens (no
> > > input event received in userspace) and no key on the keyboard works
> > > afterwards, until I press Alt. Actually the keys work, but behave as if
> > > the sysrq key was kept pressed (can be seen in dmesg, or by pressing
> > > "b").
> > > 
> > > Looking at the log, a potential culprit is commit
> > > 97f5f0cd8cd0a05449cbb77d1e6f02e026875802 (Input: implement SysRq as a
> > > separate input handler). Probably the logic of "have to press all the
> > > keys at the same time" changed to "have to press the keys one after each
> > > other". So pressing alt and later on pressing PrintScreen leads to a
> > > SysRq.
> > > 
> > > Does anybody else see this behaviour? Any suggestion on how to solve
> > > this bug? I'll try reverting the commit and report if it fixes the
> > > problem (the git revert fails so I've got to fix the conflict manually).
> > 
> > I can confirm this regression is due to
> > 97f5f0cd8cd0a05449cbb77d1e6f02e026875802: the reverting patch below
> > fixes it. And, as long as you don't press alt since boot, PrintScreen
> > works fine. So it is likely due to not taking into account key releases.
> > 
> > Dmitry, do you have a better fix? I'll be happy to test it if needed.
> > 
> 
> Not yet, but I see the effects you are describing... Stay tuned...
> 

Eric, could you tell me if the following fixes the problem for you?

Thanks!

-- 
Dmitry

Input: sysrq - fix "stuck" SysRq mode

This shoud fix the problem with SysRq mode staying half-way enabled
and interfereing with normal PrtScrn operation after user presses ALT
for the first time.

Reported-by: Éric Piel <E.A.B.Piel@tudelft.nl>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
---

 drivers/char/sysrq.c |    8 ++++++--
 1 files changed, 6 insertions(+), 2 deletions(-)


diff --git a/drivers/char/sysrq.c b/drivers/char/sysrq.c
index c046075..5bf3618 100644
--- a/drivers/char/sysrq.c
+++ b/drivers/char/sysrq.c
@@ -579,8 +579,12 @@ static bool sysrq_filter(struct input_handle *handle, unsigned int type,
 	case KEY_RIGHTALT:
 		if (value)
 			sysrq_alt = code;
-		else if (sysrq_down && code == sysrq_alt_use)
-			sysrq_down = false;
+		else {
+			if (sysrq_down && code == sysrq_alt_use)
+				sysrq_down = false;
+
+			sysrq_alt = 0;
+		}
 		break;
 
 	case KEY_SYSRQ:
--
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