Messages in this thread | | | Date | Sat, 28 Jan 2012 10:55:29 +0400 | From | Michael Tokarev <> | Subject | Re: 3.0.18 tcsetattr on fd 0 when detached freezes system (RCU timeouts) (Centos 6.1 x86_64) |
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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
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