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Top Forums Programming C Sleep function hangs @ __kernel_vsyscall () Post 302531454 by achenle on Thursday 16th of June 2011 08:36:29 PM
Old 06-16-2011
Quote:
Originally Posted by jim mcnamara
Are you blocking SIGALRM? sleep usually works by setting a timer, then sending a SIGALRM signal to the calling process.
That's normally no longer true.

And in this case, its pretty likely that sleep() has been implemented with a version of nanoslee().

It would be nice to see what the actual source code is, though.

If you look, it appears as if the file "sleep.c" calls __nanosleep_nocancel() directly. That could be something in the way libc actually links in nanosleep(), but maybe not? And if what's supposed to be an internal call is being used incorrectly, maybe the sleep time is a very large 64-bit integer - and the call does have "nocancel" appended to it....
 

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ppmtosixel(1)						      General Commands Manual						     ppmtosixel(1)

NAME
ppmtosixel - convert a portable pixmap into DEC sixel format SYNOPSIS
ppmtosixel [-raw] [-margin] [ppmfile] DESCRIPTION
Reads a portable pixmap as input. Produces sixel commands (SIX) as output. The output is formatted for color printing, e.g. for a DEC LJ250 color inkjet printer. If RGB values from the PPM file do not have maxval=100, the RGB values are rescaled. A printer control header and a color assignment table begin the SIX file. Image data is written in a compressed format by default. A printer control footer ends the image file. OPTIONS
-raw If specified, each pixel will be explicitly described in the image file. If -raw is not specified, output will default to com- pressed format in which identical adjacent pixels are replaced by "repeat pixel" commands. A raw file is often an order of magni- tude larger than a compressed file and prints much slower. -margin If -margin is not specified, the image will be start at the left margin (of the window, paper, or whatever). If -margin is speci- fied, a 1.5 inch left margin will offset the image. PRINTING
Generally, sixel files must reach the printer unfiltered. Use the lpr -x option or cat filename > /dev/tty0?. BUGS
Upon rescaling, truncation of the least significant bits of RGB values may result in poor color conversion. If the original PPM maxval was greater than 100, rescaling also reduces the image depth. While the actual RGB values from the ppm file are more or less retained, the color palette of the LJ250 may not match the colors on your screen. This seems to be a printer limitation. SEE ALSO
ppm(5) AUTHOR
Copyright (C) 1991 by Rick Vinci. 26 April 1991 ppmtosixel(1)
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