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Re: [patch-rt] drivers/zram: fix zcomp_stream_get() smp_processor_id() use in preemptible code

From Thomas Gleixner <tglx@linutronix.de>
Newsgroups linux.kernel
Subject Re: [patch-rt] drivers/zram: fix zcomp_stream_get() smp_processor_id() use in preemptible code
Date 2017-09-01 09:50 +0200
Message-ID <ukOSd-Pw-1@gated-at.bofh.it> (permalink)
References (1 earlier) <uhAC7-7kw-17@gated-at.bofh.it> <ukDap-1iX-1@gated-at.bofh.it> <ukDk6-1mJ-17@gated-at.bofh.it> <ukDtL-1q4-1@gated-at.bofh.it> <ukOSd-Pw-3@gated-at.bofh.it>
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On Fri, 1 Sep 2017, Sebastian Andrzej Siewior wrote:

> On 2017-08-31 21:32:30 [+0200], Thomas Gleixner wrote:
> > > zram_lock_table() is bit_spin_lock() on !RT and spin_lock(&table->lock);
> > > on RT. So this is done.
> > > !RT has this running in a kmap_atomic() section so they have no
> > > preemption there.
> > > zcomp_stream_get() returns a per-CPU object which is protected with a
> > > spinlock and only accessed locked.
> > 
> > So when we are inside a spinlocked section, why is this_cpu_ptr() not
> > working? That does not make sense.
> 
> zram_decompress_page() invokes zcomp_stream_get() within a spin_lock
> section (zram_lock_table()). This is fine.
> zram_bvec_write() does not invoke zcomp_stream_get() within a spin_lock
> section.

Fair enough.

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Re: [patch-rt] drivers/zram: fix zcomp_stream_get() smp_processor_id()  use in preemptible code Thomas Gleixner <tglx@linutronix.de> - 2017-08-31 21:20 +0200
  Re: [patch-rt] drivers/zram: fix zcomp_stream_get()  smp_processor_id() use in preemptible code Sebastian Andrzej Siewior <bigeasy@linutronix.de> - 2017-08-31 21:30 +0200
    Re: [patch-rt] drivers/zram: fix zcomp_stream_get() smp_processor_id()  use in preemptible code Thomas Gleixner <tglx@linutronix.de> - 2017-08-31 21:40 +0200
      Re: [patch-rt] drivers/zram: fix zcomp_stream_get() smp_processor_id()  use in preemptible code Thomas Gleixner <tglx@linutronix.de> - 2017-09-01 09:50 +0200
      Re: [patch-rt] drivers/zram: fix zcomp_stream_get()  smp_processor_id() use in preemptible code Sebastian Andrzej Siewior <bigeasy@linutronix.de> - 2017-09-01 09:50 +0200

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