Linux – Is segfault signal always sent to application

dmesglinuxsegmentation-fault

My application usually crashes and prints stack to log if received segfault signal.

But in some environment the 'dmesg' shows segfault messages related to my application, but application uptime is much older.

Can segfault be suppressed and application doesn't receive signal?
Or what errors from dmesg can mean ?

Best Answer

It is possible for an application or to ignore or do some special handling for the segmentation fault signal. The manual page for signal and related pages has details on it.

One possible situation I see could lead to the behaviour described (dmesg reports segfaults but application is running) is that the application forks and the child process segfaults. To know if this is the case, check if the process id reported by dmesg is the same as the one of the currently running process.

Related Solutions

Linux – How to diagnose frequent segfaults

Check your memory!

The most frequent cause of random segfaults like this is bad memory. Grab a memory checker (such as memtest86+) and test it.

Linux – Making TCP dump without packets loss

At your amount of traffic, I would claim that libpcap should have no trouble with dropped packets unless you have a particularly inefficient setup. If you are using tcpdump for capturing, it will report the amount of dropped packets in its final output line. If you see dropped packets, you might want to increase tcpdump's buffer size by supplying the -B option to set a value considerably higher than the default 2 MB.

Nevertheless, you might want to look at PF_RING:

Who needs PF_RING™?

Basically everyone who has to handle many packets per second. The term ‘many’ changes according to the hardware you use for traffic analysis. It can range from 80k pkt/sec on a 1,2GHz ARM to 14M pkt/sec and above on a low-end 2,5GHz Xeon. PF_RING™ not only enables you to capture packets faster, it also captures packets more efficiently preserving CPU cycles. Just to give you some figures you can see how fast nProbe, a NetFlow v5/v9 probe, can go using PF_RING™, or have a look at the tables below.

10 Gigabit tests performed on a Core2Duo 1.86 GHz and a low-end Xeon 2,5 Ghz

                                    ixgbe 
            Application                                 Rate 
pfcount (RX, with PF_RING™ DNA)        11 Mpps (Core2Duo), 14.8 Mpps (Xeon) 
pfsend (TX, with PF_RING™ DNA)         11 Mpps (Core2Duo), 14.8 Mpps (Xeon)

The PF_RING user guide explains how to compile and configure PF_RING-enabled libpcap libraries, if you insist on using libpcap applications for packet capture.

Best Answer

Related Solutions

Linux – How to diagnose frequent segfaults

Linux – Making TCP dump without packets loss

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