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Differential D39132

panic(9): some updates
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Authored by mhorne on Mar 16 2023, 7:36 PM.
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markj
kib
jhb
rpokala
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manpages
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rG86e2335d10e5: panic(9): some updates
rGd5e105bf7e4c: panic(9): some updates
Summary
  • Correct the include headers
  • Better description of what the panic() function does
  • Document KERNEL_PANICKED()
  • Add a section describing panic execution context
  • Add SEE ALSO

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rG FreeBSD src repository
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Event Timeline

mhorne created this revision.Mar 16 2023, 7:36 PM
Herald added a subscriber: imp. · View Herald TranscriptMar 16 2023, 7:36 PM
mhorne requested review of this revision.Mar 16 2023, 7:36 PM
Harbormaster completed remote builds in B50425: Diff 118947.Mar 16 2023, 7:36 PM
mhorne added a parent revision: D39131: KASSERT(9): some updates.Mar 16 2023, 7:36 PM
mhorne added a child revision: D39133: kern_reboot(9): some updates.
mhorne added reviewers: markj, kib, jhb.Mar 16 2023, 7:39 PM
markj added inline comments.Mar 16 2023, 8:04 PM
share/man/man9/panic.9
73

I would just say that it disables interrupts. spinlock_enter() just happens to be the name of the MI function used for that purpose.

87

It'd be worth mentioning debugger_on_panic IMO.

97–147

Maybe "called recursively" would be more clear?

125
129
rpokala added a subscriber: rpokala.Mar 16 2023, 8:19 PM
rpokala added inline comments.
share/man/man9/panic.9
73

When
.Fn panic
or
.Fn vpanic
is entered, the calling thread takes its spinlock.

80

In the unlikely event of concurrent panics, only one panicking thread will proceed.

85

is called to restart the system, attempting a kernel dump in the process.

mhorne updated this revision to Diff 118958.Mar 16 2023, 9:33 PM
mhorne marked 8 inline comments as done.

Handle feedback.

Harbormaster completed remote builds in B50435: Diff 118958.Mar 16 2023, 9:33 PM
mhorne added inline comments.Mar 16 2023, 9:35 PM
share/man/man9/panic.9
73

@rpokala I added a short paragraph that clarifies vpanic(), but I prefer to keep mentions of it out of the main body of the description.

@markj yes, I thought that name was somewhat suspect.

rpokala accepted this revision.Mar 16 2023, 10:04 PM
This revision is now accepted and ready to land.Mar 16 2023, 10:04 PM
kib added inline comments.Mar 17 2023, 7:11 AM
share/man/man9/panic.9
48–49

Again, traditionally it was sys/systm.h, and we should offer either of the headers as the correct one.

77

I believe the 'first time' is somewhat confusing. The situation you describe is actually the concurrent calls.

mhorne updated this revision to Diff 119026.Mar 17 2023, 6:24 PM

Handle kib's comments.

This revision now requires review to proceed.Mar 17 2023, 6:24 PM
Harbormaster completed remote builds in B50449: Diff 119026.Mar 17 2023, 6:24 PM
kib accepted this revision.Mar 17 2023, 8:00 PM
This revision is now accepted and ready to land.Mar 17 2023, 8:00 PM
rpokala accepted this revision.Mar 18 2023, 12:33 AM
markj accepted this revision.Mar 18 2023, 2:45 PM
markj added inline comments.
share/man/man9/panic.9
71–80
74

Not related to the patch, just a general question: why do spinlock_enter()/_exit() enter a critical section at all? I would expect disabling interrupts to have the same effect, at least in non-INVARIANTS kernels.

kib added inline comments.Mar 18 2023, 3:32 PM
share/man/man9/panic.9
74

To prevent context switches in the code executed under spinlock. As an example, imagine that some code took a spinlock, then does critical_enter()/critical_exit(). If owe_preempt is set, we end up trying to reschedule.

markj added inline comments.Mar 18 2023, 3:39 PM
share/man/man9/panic.9
74

Oops, of course. Thanks.

Closed by commit rGd5e105bf7e4c: panic(9): some updates (authored by mhorne). · Explain WhyMar 20 2023, 8:13 PM
This revision was automatically updated to reflect the committed changes.
mhorne marked an inline comment as done.
mhorne added a commit: rGd5e105bf7e4c: panic(9): some updates.
mhorne added a commit: rG86e2335d10e5: panic(9): some updates.Mar 27 2023, 5:22 PM

Revision Contents
Changeset List

PathSize
share/
man/
man9/
3 lines
109 lines

Diff 119145

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share/man/man9/Makefile

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share/man/man9/panic.9

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