CODEWITHSUNDEEP
cmultithreadingdebuggingsignals
user34790
user34790

Reputation: 2036

Debugging signal handling in multithreaded application

I have this multithreaded application using pthreads. My threads actually wait for signals using sigwait. Actually, I want to debug my application, see which thread receives which signal at what time and then debug it. Is there any method, I can do this. If I directly run my program, then signals are generated rapidly and handled by my handler threads. I want to see which handler wakes up from the sigwait call and processes the signal and all.

Upvotes: 0

Views: 703

Answers (2)

sirgeorge
sirgeorge

Reputation: 6541

One of the things you may try with gdb is set breakpoints by thread (e.g. just after return from sigwait), so you know which thread wakes up:

break file.c thread [thread_nr]

Don't forget to tell gdb to pass signals to your program e.g.:

handle SIGINT pass

You may want to put all of this into your .gdbinit file to save yourself a lot of typing.

Steven Schlansker is definitely right: if that happens to significantly change timing patterns of your program (so you can see that your program behaves completely different under debugger, than "in the wild") then strace and logging is your last hope. I hope that helps.

Upvotes: 0

Steven Schlansker
Steven Schlansker

Reputation: 38526

The handy strace utility can print out a huge amount of useful information regarding system calls and signals. It would be useful to log timing information or collect statistics regarding the performance of signal usage.

If instead you are interested in getting a breakpoint inside of an event triggered by a specific signal, you could consider stashing enough relevant information to identify the event in a variable and setting a conditional breakpoint.

Upvotes: 1

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