Properly handle event ordering constraints for core dump signals #2493
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The order of events for coredumping signals is extremely confusing, so I got it slightly wrong. This commit attempts to remidy that. For my future reference, here are some breadcrumbs of how the event ordering works for coredumping signals: 1) The thread that receives the coredumping signal will block (without further event after the injection), until all other threads have passed their exit events [1] 2) After passing their own exit events, all other threads will block until the coredump is complete (equivalently until all threads have passed their exit events). Note that in this state, these tasks are also ignoring SIGKILL. 3) Once the coredump is complete, each task may proceed. The first task to its exit events, the other tasks to their zombie state. Of course hidden zombie state applies for exits by thread group leaders. [1] https://github.com/torvalds/linux/blob/7e63420847ae5f1036e4f7c42f0b3282e73efbc2/fs/coredump.c#L457 [2] https://github.com/torvalds/linux/blob/7e63420847ae5f1036e4f7c42f0b3282e73efbc2/kernel/exit.c#L461-L466
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The order of events for coredumping signals is extremely confusing,
so I got it slightly wrong. This commit attempts to remidy that.
For my future reference, here are some breadcrumbs of how the
event ordering works for coredumping signals:
further event after the injection), until all other threads have passed
their exit events [1]
the coredump is complete (equivalently until all threads have passed their
exit events). Note that in this state, these tasks are also ignoring SIGKILL.
its exit events, the other tasks to their zombie state.
Of course hidden zombie state applies for exits by thread group leaders.
[1] https://github.com/torvalds/linux/blob/7e63420847ae5f1036e4f7c42f0b3282e73efbc2/fs/coredump.c#L457
[2] https://github.com/torvalds/linux/blob/7e63420847ae5f1036e4f7c42f0b3282e73efbc2/kernel/exit.c#L461-L466