Messages in this thread | | | Date | Wed, 13 Nov 2019 12:44:14 +0100 | From | Borislav Petkov <> | Subject | Re: [PATCH] x86/resctrl: Fix potential lockdep warning |
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On Thu, Nov 07, 2019 at 06:36:36AM +0800, Xiaochen Shen wrote: > rdtgroup_cpus_write() and mkdir_rdt_prepare() call > rdtgroup_kn_lock_live() -> kernfs_to_rdtgroup() to get 'rdtgrp', and > then call rdt_last_cmd_xxx() functions which will check if
Write those names like this:
rdt_last_cmd_{clear,puts,...} but not with an "xxx" which confuses people unfamiliar with the code.
> rdtgroup_mutex is held/requires its caller to hold rdtgroup_mutex. > But if 'rdtgrp' returned from kernfs_to_rdtgroup() is NULL, > rdtgroup_mutex is not held and calling rdt_last_cmd_xxx() will result > in a lockdep warning.
That's more of a self-incurred lockdep warning. You can't be calling lockdep_assert_held() after a function which doesn't always grab the mutex. Looks like the design needs changing here...
> Remove rdt_last_cmd_xxx() in these two paths. Just returning error > should be sufficient to report to the user that the entry doesn't exist > any more.
... or that.
In any case, you should consider fixing such patterns in the code as it looks sub-optimal from where I'm standing.
Thx.
-- Regards/Gruss, Boris.
https://people.kernel.org/tglx/notes-about-netiquette
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