Messages in this thread | ![/](/images/icornerl.gif) | | Date | Wed, 6 May 2015 15:01:58 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH RFC 00/15] decouple pagefault_disable() from preempt_disable() |
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On Wed, 6 May 2015 19:50:24 +0200 David Hildenbrand <dahi@linux.vnet.ibm.com> wrote:
> As Peter asked me to also do the decoupling in one shot, this is > the new series. > > I recently discovered that might_fault() doesn't call might_sleep() > anymore. Therefore bugs like: > > spin_lock(&lock); > rc = copy_to_user(...); > spin_unlock(&lock); > > would not be detected with CONFIG_DEBUG_ATOMIC_SLEEP. The code was > changed to disable false positives for code like: > > pagefault_disable(); > rc = copy_to_user(...); > pagefault_enable(); > > Whereby the caller wants do deal with failures.
hm, that was a significant screwup. I wonder how many bugs we subsequently added.
> > .. >
> This series therefore does 2 things: > > > 1. Decouple pagefault_disable() from preempt_enable() > > ... > > 2. Reenable might_sleep() checks for might_fault()
All seems sensible to me. pagefault_disabled has to go into the task_struct (rather than being per-cpu) because pagefault_disabled_inc() doesn't disable preemption, yes?
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