* 3.0.18 tcsetattr on fd 0 when detached freezes system (RCU timeouts) (Centos 6.1 x86_64)
@ 2012-01-28 0:43 Professor Berkley Shands
2012-01-28 6:55 ` Michael Tokarev
0 siblings, 1 reply; 4+ messages in thread
From: Professor Berkley Shands @ 2012-01-28 0:43 UTC (permalink / raw)
To: linux-kernel
typedef struct
{
struct termios term;
} XKEY_DATA;
typedef XKEY_DATA *xkeyhandle;
static inline xkeyhandle xkeystart()
{
// Turn off echo.
struct termios temp;
err = tcgetattr(0, &temp);
if (err)
{
perror("tcgetattr failure");
}
XKEY_DATA *handle = new XKEY_DATA;
handle->term = temp;
temp.c_lflag &= ~ECHO;
temp.c_lflag &= ~ICANON;
err = tcsetattr(0, TCSANOW, &temp); // this line causes the
kernel to get very sick
if (err)
{
perror("tcsetattr failure");
}
return handle;
}
The above code, called from main() will produce an error from tcsh:
/home/bshands> ./a.out > /dev/null &
[1] 3635
/home/bshands>
/home/bshands>
[1] + Suspended (tty output) ./a.out > /dev/null
/home/bshands>
this does not appear on the redhat kernel, nor 2.6.32.43, but appeared
infrequently in 3.0.9.
in 3.0.18, doing this in the background does *EVIL* things.
ssh system "./a.out > /dev/null &" &
Now when the code reaches the tcsetattr() the system quits scheduling tasks.
top shows 100%sy on 4/12 cores, kernel threads blocked, stalled tasks
count increasing.
Jan 27 18:58:50 system kernel: [ 1269.891610] kjournald S
ffff880321270a30 0 416 2 0x00000000
Jan 27 18:58:50 system kernel: [ 1269.891684] ffff880321f5de50
0000000000000046 ffff880321270680 0000000000000000
Jan 27 18:58:50 system kernel: [ 1269.891816] ffff880321270680
0000000000012ac0 ffff880321f5dfd8 ffff880321f5c010
Jan 27 18:58:50 system kernel: [ 1269.891948] ffff880321f5dfd8
0000000000012ac0 ffff880327a61260 ffff880321270680
Jan 27 18:58:50 system kernel: [ 1269.892083] Call Trace:
Jan 27 18:58:50 system kernel: [ 1269.892144] [<ffffffff824c126f>]
schedule+0x3f/0x60
Jan 27 18:58:50 system kernel: [ 1269.892226] [<ffffffffa0030f9d>]
kjournald+0x20d/0x230 [jbd]
Jan 27 18:58:50 system kernel: [ 1269.892294] [<ffffffff82082230>] ?
wake_up_bit+0x40/0x40
Jan 27 18:58:50 system kernel: [ 1269.892362] [<ffffffffa0030d90>] ?
commit_timeout+0x10/0x10 [jbd]
Jan 27 18:58:50 system kernel: [ 1269.892431] [<ffffffff82081bb6>]
kthread+0x96/0xa0
Jan 27 18:58:50 system kernel: [ 1269.892497] [<ffffffff824cbe04>]
kernel_thread_helper+0x4/0x10
Jan 27 18:58:50 system kernel: [ 1269.892565] [<ffffffff82081b20>] ?
kthread_worker_fn+0x1a0/0x1a0
Jan 27 18:58:50 system kernel: [ 1269.892633] [<ffffffff824cbe00>] ?
gs_change+0x13/0x13
After a little while, the system locks up. rcu timeout errors may appear
in dmesg.
dumps are available.
Note that this little bugger is a user mode crash, once started, you are
done.
it appears that later use of termios is still sufficient to trigger the
lockup.
they key is being detached.
Berkley
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: 3.0.18 tcsetattr on fd 0 when detached freezes system (RCU timeouts) (Centos 6.1 x86_64)
2012-01-28 0:43 3.0.18 tcsetattr on fd 0 when detached freezes system (RCU timeouts) (Centos 6.1 x86_64) Professor Berkley Shands
@ 2012-01-28 6:55 ` Michael Tokarev
[not found] ` <4F283B40.1070200@seas.wustl.edu>
0 siblings, 1 reply; 4+ messages in thread
From: Michael Tokarev @ 2012-01-28 6:55 UTC (permalink / raw)
To: Professor Berkley Shands; +Cc: linux-kernel
On 28.01.2012 04:43, Professor Berkley Shands wrote:
>
> typedef struct
> {
> struct termios term;
> } XKEY_DATA;
>
> typedef XKEY_DATA *xkeyhandle;
>
> static inline xkeyhandle xkeystart()
> {
>
> // Turn off echo.
> struct termios temp;
> err = tcgetattr(0, &temp);
> if (err)
> {
> perror("tcgetattr failure");
> }
>
> XKEY_DATA *handle = new XKEY_DATA;
> handle->term = temp;
>
> temp.c_lflag &= ~ECHO;
> temp.c_lflag &= ~ICANON;
>
> err = tcsetattr(0, TCSANOW, &temp); // this line causes the kernel to get very sick
> if (err)
> {
> perror("tcsetattr failure");
> }
>
> return handle;
>
> }
>
> The above code, called from main() will produce an error from tcsh:
>
> /home/bshands> ./a.out > /dev/null &
> [1] 3635
> /home/bshands>
> /home/bshands>
> [1] + Suspended (tty output) ./a.out > /dev/null
> /home/bshands>
>
> this does not appear on the redhat kernel, nor 2.6.32.43, but appeared infrequently in 3.0.9.
> in 3.0.18, doing this in the background does *EVIL* things.
>
> ssh system "./a.out > /dev/null &" &
>
> Now when the code reaches the tcsetattr() the system quits scheduling tasks.
> top shows 100%sy on 4/12 cores, kernel threads blocked, stalled tasks count increasing.
I used the following code:
=======================================
#include <termios.h>
#include <stdio.h>
int main() {
struct termios temp;
if (tcgetattr(0, &temp) != 0)
perror("tcgetattr failure");
temp.c_lflag &= ~ECHO;
temp.c_lflag &= ~ICANON;
if (tcsetattr(0, TCSANOW, &temp) != 0) // this line causes the kernel to get very sick
perror("tcsetattr failure");
return 0;
}
=======================================
But can't reproduce what you're observing. It prints
tcgetattr failure: Inappropriate ioctl for device
tcsetattr failure: Inappropriate ioctl for device
and does not do any evil things. I tried it on 3.0.18
on x86 on 32bits and 64bits.
What I'm doing wrong?
Thanks,
/mjt
^ permalink raw reply [flat|nested] 4+ messages in thread
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2012-01-28 0:43 3.0.18 tcsetattr on fd 0 when detached freezes system (RCU timeouts) (Centos 6.1 x86_64) Professor Berkley Shands
2012-01-28 6:55 ` Michael Tokarev
[not found] ` <4F283B40.1070200@seas.wustl.edu>
2012-02-02 8:36 ` Michael Tokarev
2012-02-02 22:09 ` Professor Berkley Shands
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