Luckily this problem don’t happen so frequently, at least using stable kernel and distributions, but sometime your beloved Linux could go in “Kernel Panic”.
A kernel panic is an action taken by an operating system upon detecting an internal fatal error from which it cannot safely recover. The term is largely specific to Unix and Unix-like systems; for Microsoft Windows operating systems the equivalent term is “stop error” (or, colloquially BSOD “Blue Screen of Death”).
The kernel routines that handle panics, known as panic() in AT&T-derived and BSD Unix source code, are generally designed to output an error message to the console, dump an image of kernel memory to disk for post-mortem debugging and then either wait for the system to be manually rebooted, or initiate an automatic reboot.
The default it’s to wait, so if this happen on one of your servers and you don’t notice it all its services could stay down for some time, while using an automatic reboot the problem could be solved quickly.