[RFC][PATCH] Replace a function call chain of kmsg_dump(KMSG_DUMP_KEXEC) with static function calls
Américo Wang
xiyou.wangcong at gmail.com
Wed Jul 13 04:37:12 EDT 2011
2011/7/11 Seiji Aguchi <seiji.aguchi at hds.com>:
> Hi,
>
Hi,
>
> [Patch Description]
>
> For meeting Eric/Vivek's requirements and solving issues of pstore/efivars driver, I propose a following patch.
>
> - Remove kmsg_dump(KMSG_DUMP_KEXEC) from crash_kexec()
It is already removed in -mm, can you rebase your patch against -mm?
> - Add kmsg_dump_kexec() to crash_kexec()
> kmsg_dump_kexec() moved behind machine_crash_shutdown() so that
> we can output kernel messages without getting any locks.
>
> - Introduce CONFIG_KMSG_DUMP_KEXEC
> - CONFIG_KMSG_DUMP_KEXEC depends on CONFIG_PRINTK which is required for kmsg_dumper.
>
> - CONFIG_KMSG_DUMP_KEXEC=n (default)
> Kernel message logging feature doesn't work in kdump path.
>
> - CONFIG_KMSG_DUMP_KEXEC=y
> following static functions are called in kdump path.
> - kmsg_dump_kexec(): This is based on kmsg_dump() and just removed spinlock and a function call chain from it.
> - do_kmsg_dump_kexec(): This is based on pstore_dump() and just removed mutex lock from it.
>
> Some people who are not familiar with kexec may add function calls getting spin_lock/mutex_lock in kexec path.
> These function calls causes failure of kexec.
> So, I suggest replace a call chain with static function calls so that we can keep reliability of kexec.
>
> - Add efi_kmsg_dump_kexec() which outputs kernel messages into NVRAM with EFI.
> This is called by do_kmsg_dump_kexec() statically.
> By applying to Matthew Garret's patch below, its kernel messages in NVRAM are visible through /dev/pstore.
This looks weird, kmsg_dump_kexec() calls do_kmsg_dump_kexec()
which then calls efi_kmsg_dump_kexec(), so, why not just call
efi_kmsg_dump_kexec()?
since there is no other user of kmsg_dump_kexec().
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