8c5a9161d1
Save the last callout function pointer (and its argument) executed on each CPU for inspection by a debugger. Add a ddb `show callout_last` command to show these pointers. Add a kernel module that I used for testing that command. Relocate `ce_migration_cpu` to reduce padding and therefore preserve the size of `struct callout_cpu` (320 bytes on amd64) despite the added members. This should help diagnose reference-after-free bugs where the callout's mutex has already been freed when `softclock_call_cc` tries to unlock it. You might hope that the pointer would still be available, but it isn't. The argument to that function is on the stack (because `softclock_call_cc` uses it later), and that might be enough in some cases, but even then, it's very laborious. A pointer to the callout is saved right before these newly added fields, but that callout might have been freed. We still have the pointer to its associated mutex, and the name within might be enough, but it might also have been freed. Reviewed by: markj jhb MFC after: 2 weeks Sponsored by: Dell EMC Isilon Differential Revision: https://reviews.freebsd.org/D20794
7 lines
77 B
Makefile
7 lines
77 B
Makefile
# $FreeBSD$
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KMOD= callout_free
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SRCS= callout_free.c
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.include <bsd.kmod.mk>
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