Best way to handle SIGKILL in Linux kernel

Question

I'm writing a syscall in Linux 3.0, and while I wait for some event to occur (using a waitqueue), I would like to check for a pending SIGKILL and if one occurs, I would like for the current task to die as soon as possible. As far as I can tell, as soon as I return from the syscall (well, really: as soon as the process is to enter into user mode) returns, the kernel checks for pending signals and upon seeing the SIGKILL, the kernel will kill current before it returns to user mode.

Question: Is my above assumption correct about how SIGKILL works? My other option is to see that the fatal SIGKILL is pending, and instead of returning from the syscall, I just perform a do_exit(). I'd like to be as consistent as possible with other Linux use cases...and it appears that simply returning from the syscall is what other code does. I just want to ensure that the above assumption about how SIGKILL kills the task is correct.

adobriyan · Accepted Answer · 2012-08-31 11:10:58Z

1

Signal checking happens after system call exit, yes.

See e.g. ret_from_sys_call at arch/x86/kernel/entry_64.S.

answered Aug 31, 2012 at 11:10

adobriyan

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