3.4.2 デッドロックの可能性があるが正常終了する実行の検証

食事する哲学者プログラムは、十分なスリープ引数値を指定すると、実デッドロックを回避し、正常に終了することができます。ただし、正常終了は、プログラムがデッドロックにならないことを意味するわけではありません。単に、実行中に、保持および要求されたロックによってデッドロックチェーンが形成されなかっただけです。別の実行でタイミングが変われば、実デッドロックが発生する可能性があります。次のリストは、食事する哲学者プログラムが正常終了する実行を示しています。ただし、er_print ユーティリティーとスレッドアナライザからは潜在的デッドロックが報告されます。

% cc din_philo.c -mt -g                


% collect -r deadlock a.out 40
Creating experiment database tha.2.er ...
Philosopher 0 is done thinking and now ready to eat.
Philosopher 2 is done thinking and now ready to eat.
Philosopher 1 is done thinking and now ready to eat.
Philosopher 3 is done thinking and now ready to eat.
Philosopher 2: got right  chopstick 2
Philosopher 3: got right  chopstick 3
Philosopher 0: got right  chopstick 0
Philosopher 4 is done thinking and now ready to eat.
Philosopher 0: got left chopstick 1
Philosopher 0: eating.
Philosopher 3: got left chopstick 4
Philosopher 3: eating.
Philosopher 0: got right  chopstick 0
Philosopher 4: got right  chopstick 4
Philosopher 2: got left chopstick 3
Philosopher 2: eating.
Philosopher 0: got left chopstick 1
Philosopher 0: eating.
Philosopher 3: got right  chopstick 3
Philosopher 2: got right  chopstick 2
Philosopher 4: got left chopstick 0
Philosopher 4: eating.
Philosopher 0: got right  chopstick 0
Philosopher 3: got left chopstick 4
Philosopher 3: eating.
Philosopher 0: got left chopstick 1
Philosopher 0: eating.
Philosopher 4: got right  chopstick 4
Philosopher 2: got left chopstick 3
Philosopher 2: eating.
Philosopher 4: got left chopstick 0
Philosopher 4: eating.
Philosopher 3: got right  chopstick 3
Philosopher 2: got right  chopstick 2
Philosopher 0: got right  chopstick 0
Philosopher 3: got left chopstick 4
Philosopher 3: eating.
Philosopher 0: got left chopstick 1
Philosopher 0: eating.
Philosopher 0: got right  chopstick 0
Philosopher 2: got left chopstick 3
Philosopher 2: eating.
...
Philosopher 0: got left chopstick 1
Philosopher 0: eating.
Philosopher 4: got right  chopstick 4
Philosopher 3: got right  chopstick 3
Philosopher 4: got left chopstick 0
Philosopher 4: eating.
Philosopher 0: got right  chopstick 0
Philosopher 3: got left chopstick 4
Philosopher 0: got left chopstick 1
Philosopher 0: eating.
Philosopher 3: eating.
Philosopher 0: got right  chopstick 0
Philosopher 2: got left chopstick 3
Philosopher 2: eating.
Philosopher 0: got left chopstick 1
Philosopher 0: eating.
Philosopher 4: got right  chopstick 4
Philosopher 3: got right  chopstick 3
Philosopher 2: got right  chopstick 2
Philosopher 4: got left chopstick 0
Philosopher 4: eating.
Philosopher 4 is done eating.
Philosopher 3: got left chopstick 4
Philosopher 3: eating.
Philosopher 0: got right  chopstick 0
Philosopher 0: got left chopstick 1
Philosopher 0: eating.
Philosopher 3 is done eating.
Philosopher 2: got left chopstick 3
Philosopher 2: eating.
Philosopher 0 is done eating.
Philosopher 2 is done eating.
Philosopher 1: got right  chopstick 1
Philosopher 1: got left chopstick 2
Philosopher 1: eating.
Philosopher 1 is done eating.
%

実行は正常に終了します


% er_print tha.2.er 
(er_print) deadlocks

デッドロック #1, 潜在的デッドロック
	スレッド #2
		ロック保持中:	0x215a8, 位置: grab_chopstick + 0x0000002C, 行 101 "din_philo.c"
		ロック要求中:	0x215c0, 位置: grab_chopstick + 0x0000002C, 行 101 "din_philo.c"
	スレッド #3
		ロック保持中:	0x215c0, 位置: grab_chopstick + 0x0000002C, 行 101 "din_philo.c"
		ロック要求中:	0x215d8, 位置: grab_chopstick + 0x0000002C, 行 101 "din_philo.c"
	スレッド #4
		ロック保持中:	0x215d8, 位置: grab_chopstick + 0x0000002C, 行 101 "din_philo.c"
		ロック要求中:	0x215f0, 位置: grab_chopstick + 0x0000002C, 行 101 "din_philo.c"
	スレッド #5
		ロック保持中:	0x215f0, 位置: grab_chopstick + 0x0000002C, 行 101 "din_philo.c"
		ロック要求中:	0x21608, 位置: grab_chopstick + 0x0000002C, 行 101 "din_philo.c"
	スレッド #6
		ロック保持中:	0x21608, 位置: grab_chopstick + 0x0000002C, 行 101 "din_philo.c"
		ロック要求中:	0x215a8, 位置: grab_chopstick + 0x0000002C, 行 101 "din_philo.c"

デッドロック一覧の概要: 実験: tha.2.er 総デッドロック数: 1
(er_print) 
 

次のスクリーンショットは、スレッドアナライザインタフェースに表示された潜在的ロック情報を示しています。