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Full Discussion: Semaphore
Top Forums UNIX for Beginners Questions & Answers Semaphore Post 303015714 by Corona688 on Tuesday 10th of April 2018 02:51:44 PM
Old 04-10-2018
Quote:
Originally Posted by uniran
I didn't get it, which is the critical section?
Exactly what you think it is.
Quote:
How would a thread wake up in order to enter it if the post comes after this critical section?
You have it a bit backwards, I think - sem_wait is what's responsible for making threads sleep. If the resource is busy, sem_wait makes you sleep, if the resource is free, it does not.

The first thread to enter the critical section does not sleep and the semaphore is decremented from 1 to 0. The second and third threads cannot decrement the semaphore and are forced to wait instead.

The first thread, which didn't stop, keeps going and eventually runs sem_post, which wakes up the second thread, which runs and eventually runs sem_post, et cetera.
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Graphics::Primitive::Insets(3pm)			User Contributed Perl Documentation			  Graphics::Primitive::Insets(3pm)

NAME
Graphics::Primitive::Insets - Space between things DESCRIPTION
Graphics::Primitive::Insets represents the amount of space that surrounds something. This object can be used to represent either padding or margins (in the CSS sense, one being inside the bounding box, the other being outside) SYNOPSIS
use Graphics::Primitive::Insets; my $insets = Graphics::Primitive::Insets->new({ top => 5, bottom => 5, left => 5, right => 5 }); METHODS
Constructor new Creates a new Graphics::Primitive::Insets. Instance Methods as_array Return these insets as an array in the form of top, right, bottom and left. bottom Set/Get the inset from the bottom. equal_to Determine if these Insets are equal to another. left Set/Get the inset from the left. right Set/Get the inset from the right. top Set/Get the inset from the top. zero Sets all the insets (top, left, bottom, right) to 0. AUTHOR
Cory Watson, "<gphat@cpan.org>" SEE ALSO
perl(1) COPYRIGHT &; LICENSE Copyright 2008-2010 by Cory G Watson. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself. perl v5.12.3 2010-08-21 Graphics::Primitive::Insets(3pm)
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