The dining philosophers program can avoid actual deadlock and terminate
normally if you supply a large enough sleep argument. Normal termination,
however, does not mean the program is safe from deadlocks. It simply means
that the locks held and requested did not form a deadlock chain during a given
run. If the timing changes in other runs, an actual deadlock can occur. The
following listing shows a run of the dining philosophers program that terminates
normally. However, the er_print
utility and the
Thread Analyzer report potential deadlocks.
% 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. % Execution terminated normally % er_print tha.2.er (er_print) deadlocks Deadlock #1, Potential deadlock Thread #2 Lock being held: 0x215a8, at: grab_chopstick + 0x0000002C, line 101 in "din_philo.c" Lock being requested: 0x215c0, at: grab_chopstick + 0x0000002C, line 101 in "din_philo.c" Thread #3 Lock being held: 0x215c0, at: grab_chopstick + 0x0000002C, line 101 in "din_philo.c" Lock being requested: 0x215d8, at: grab_chopstick + 0x0000002C, line 101 in "din_philo.c" Thread #4 Lock being held: 0x215d8, at: grab_chopstick + 0x0000002C, line 101 in "din_philo.c" Lock being requested: 0x215f0, at: grab_chopstick + 0x0000002C, line 101 in "din_philo.c" Thread #5 Lock being held: 0x215f0, at: grab_chopstick + 0x0000002C, line 101 in "din_philo.c" Lock being requested: 0x21608, at: grab_chopstick + 0x0000002C, line 101 in "din_philo.c" Thread #6 Lock being held: 0x21608, at: grab_chopstick + 0x0000002C, line 101 in "din_philo.c" Lock being requested: 0x215a8, at: grab_chopstick + 0x0000002C, line 101 in "din_philo.c" Deadlocks List Summary: Experiment: tha.2.er Total Deadlocks: 1 (er_print)
The following screen-shot shows the potential deadlock information in the Thread Analyzer interface: