Questions tagged [semaphore]
The semaphore tag has no summary.
22 questions
0
votes
1
answer
294
views
How does the Kernel implement synchronisation techniques on file access
I've read that the kernel implements synchronisation mechanisms when accessing files. For example, if we try and write or read to a file in the file system using read() or write() from different ...
- 1,233
0
votes
1
answer
4k
views
How to open an existing named semaphore?
Obviously O_CREAT and O_EXCL are not required when opening an existing semaphore.
O_CREAT is required when creating a new semaphore.
O_EXCL is only meaningful when OR-ing with O_CREAT, specifying that ...
- 121
0
votes
1
answer
633
views
Adding 'Progress bar / counter' to a parallelised For Loop
I've been greatly inspired by this question: Parallelize a Bash FOR Loop to parallelise some tools I've written that involve very loooong while read loops (ie doing the same task / set of tasks ...
user279851
2
votes
2
answers
2k
views
FIFO-based semaphore explanation
I am trying to work on some parallelization of many processes (task send/to be executed on many (let's say hundreds) nodes).
I came across this solution:
https://unix.stackexchange.com/a/216475
# ...
1
vote
1
answer
438
views
GNU Parallel Python Semaphore
I have a Python script parallelized through GNU parallel which finds a certain result which I would like to output to a file, which I currently do through standard Python file IO. The issue is that I ...
1
vote
0
answers
864
views
Limit the number of thread in a parallel Bash script
I try to improve with semaphores some photo processing script I use. I run sable GNU/DEBIAN
There is a function called travail that uses a given filename as an argument, and that processes the file.
...
- 11
3
votes
1
answer
214
views
Obtaining and returning a permit from a semaphore in a shell script
In a shell script I can use:
ipcmk -S 4
To create a semaphore with 4 slots. With ipcrm I could delete the semaphore again. But how can I use it? I cannot find any semwait, ipcsemget or similar. How ...
- 1,040
0
votes
3
answers
5k
views
mutex and semaphore like in shell script [closed]
proc1.sh
#!/bin/sh
touch /tmp/proc1.signature.mutex
#do something for long time
sleep 100
rm -rf /tmp/proc1.signature.mutex
proc2.sh
#!/bin/sh
touch /tmp/proc2.signature.mutex
#do something for ...
- 11
0
votes
2
answers
2k
views
What are the benefits of mutex over semaphore in linux system programming [closed]
if binary semaphore can protect a resource atomically, then what is the benefit of mutex.
For example,
sem_init(&sem, 0, 1);
sem_wait(&sem);
critical session;
sem_post(&sem);
Please ...
- 25
2
votes
0
answers
295
views
How to fetch semaphores and sharedmem objects for a specific apache instance when more than one apache instances run with the same app id on the box
Not sure if the question is pertinent for this forum.
We have a server with 3 apache instances running with the "same" app/functional ID
These instances communicate with their corresponding ...
- 19
2
votes
0
answers
627
views
How to synchronize the initialization of unnamed POSIX semaphores?
In order to use unnamed POSIX semaphores with multiple processes one has to create/obtain access to a portion of shared memory.
After that, one process has to initialize the semaphore by calling ...
- 666
5
votes
2
answers
4k
views
Using `sem` to make a script run in parallel
I have the following shell script (one liner), which I wanted to use to identify directories that have the exact same contents. I'm using it, to identify and remove duplicate (child) directories.
...
- 231
4
votes
2
answers
10k
views
Where is a named semaphore stored? [closed]
A named semaphore (using semaphore.h) is identified by a name in the form /somename; that is, a null-terminated string of up to NAME_MAX-4 (i.e., 251) characters consisting of an initial slash, ...
- 79
19
votes
2
answers
14k
views
Performing atomic write operations in a file in bash
After going through the bash documentation, this question and this one it's still not clear to me how can I perform atomic write (append) operations to a file in bash. I have a script that is run in ...
- 1,039
4
votes
0
answers
288
views
process waiting for a semaphore
If I have a process that is in sleep state and I can see in ps column WCHAN that is waiting to obtain a semaphore, is there any way to find the address of that semaphore?
- 51