Messages in this thread | | | Date | Wed, 18 Dec 2019 12:28:01 -0800 | From | Davidlohr Bueso <> | Subject | Re: [PATCH] rxrpc: struct mutex cannot be used for rxrpc_call::user_mutex |
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On Wed, 18 Dec 2019, Davidlohr Bueso wrote:
>On Wed, 18 Dec 2019, Peter Zijlstra wrote: > >>On Tue, Dec 17, 2019 at 03:32:00PM +0000, David Howells wrote: >>>Standard kernel mutexes cannot be used in any way from interrupt or softirq >>>context, so the user_mutex which manages access to a call cannot be a mutex >>>since on a new call the mutex must start off locked and be unlocked within >>>the softirq handler to prevent userspace interfering with a call we're >>>setting up. >>> >>>Commit a0855d24fc22d49cdc25664fb224caee16998683 ("locking/mutex: Complain >>>upon mutex API misuse in IRQ contexts") causes big warnings to be splashed >>>in dmesg for each a new call that comes in from the server. >> >>FYI that patch has currently been reverted. >> >>commit c571b72e2b845ca0519670cb7c4b5fe5f56498a5 (tip/locking/urgent, tip/locking-urgent-for-linus) > >Will we ever want to re-add this warning (along with writer rwsems) at some point? > >It seems that having it actually prompts things getting fixed, as opposed to >just sitting there forever borken (at least in -rt).
Hmm so fyi __crash_kexec() is another one, but can be called in hard-irq, and it's extremely obvious that the trylock+unlock occurs in the same context.
It would be nice to automate this...
Thanks, Davidlohr
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