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Top Forums UNIX for Advanced & Expert Users Playing with the Linux Scheduler Post 302566489 by galanom on Thursday 20th of October 2011 12:31:49 PM
Old 10-20-2011
You can't come and go between user and kernel space.
These spaces are strictly separated.
The only form of communication from user space to kernelspace is with system calls.

User level threads (pthreads) create processes that run on userspace. They don't know what happens in kernel.

So to (1) no you can't know when or who scheduled the thread. If you mean when was created, then you have to provide this information on yourself on thread creation. man 7 pthreads shows shat info are stored and it basically ids, signals etc.

Also (2) you can't know if the thread is running or stopped (but you can know if it finished with nonblocking pthread_tryjoin_np()). However kernel does know, and publishes info on /proc fs (the same info you access with ps).

Finally, (3) you can't have context switching information from userspace (pthreads). Context switching is a kernel job. It is completely transparent to the userland. Of course, you can anytime give up processor from userspace with sched_yield() or from kernelspace by calling directly the scheduler with schedule() [i think].

As for scheduler, it resides at /usr/src/linux/kernel/sched.c
But it's a huge -- it's about 10k lines, you must really know what you are doing. And certainly with proper documentation.

ps: you can crash your machine very easily. There is no protection in kernel space. Try to find a program like vmware.

What do you want to do?
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merge_fonts(3alleg4)						  Allegro manual					      merge_fonts(3alleg4)

NAME
merge_fonts - Merges two fonts into one font. Allegro game programming library. SYNOPSIS
#include <allegro.h> FONT *merge_fonts(FONT *f1, FONT *f2) DESCRIPTION
This function merges the character ranges from two fonts and returns a new font containing all characters in the old fonts. In general, you cannot merge fonts of different types (eg, TrueType fonts and bitmapped fonts), but as a special case, this function can promote a mono- chrome bitmapped font to a color font and merge those. Example: FONT *myfont; FONT *myfancy_font; FONT *lower_range; FONT *upper_range; FONT *capitals; FONT *combined_font; FONT *tempfont; ... /* Create a font that contains the capitals from */ /* the fancy font but other characters from myfont */ lower_range = extract_font_range(myfont, -1, 'A'-1); upper_range = extract_font_range(myfont, 'Z'+1, -1); capitals = extract_font_range(myfancy_font, 'A', 'Z'); tempfont = merge_fonts(lower_range, capitals); combined_font = merge_fonts(tempfont, upper_range); /* Clean up temporary fonts */ destroy_font(lower_range); destroy_font(upper_range); destroy_font(capitals); destroy_font(tempfont); RETURN VALUE
Returns a pointer to the new font or NULL on error. Remember that you are responsible for destroying the font when you are finished with it to avoid memory leaks. SEE ALSO
extract_font_range(3alleg4), is_trans_font(3alleg4), is_color_font(3alleg4), is_mono_font(3alleg4), exfont(3alleg4) Allegro version 4.4.2 merge_fonts(3alleg4)
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