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From:   Thomas Gleixner <tglx@linutronix.de>
To:     Ira Weiny <ira.weiny@intel.com>
Cc:     Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Andy Lutomirski <luto@kernel.org>, x86@kernel.org,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Dan Williams <dan.j.williams@intel.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Fenghua Yu <fenghua.yu@intel.com>, linux-doc@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-nvdimm@lists.01.org,
        linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
        linux-kselftest@vger.kernel.org
Subject: Re: [PATCH RFC V3 6/9] x86/entry: Pass irqentry_state_t by reference
In-Reply-To: <20201019202647.GD3713473@iweiny-DESK2.sc.intel.com>
References: <20201009194258.3207172-1-ira.weiny@intel.com> <20201009194258.3207172-7-ira.weiny@intel.com> <20201016114510.GO2611@hirez.programming.kicks-ass.net> <87lfg6tjnq.fsf@nanos.tec.linutronix.de> <20201019053639.GA3713473@iweiny-DESK2.sc.intel.com> <87k0vma7ct.fsf@nanos.tec.linutronix.de> <20201019202647.GD3713473@iweiny-DESK2.sc.intel.com>
Date:   Mon, 19 Oct 2020 23:12:44 +0200
Message-ID: <871rhtapir.fsf@nanos.tec.linutronix.de>
MIME-Version: 1.0
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Precedence: bulk

On Mon, Oct 19 2020 at 13:26, Ira Weiny wrote:
> On Mon, Oct 19, 2020 at 11:32:50AM +0200, Thomas Gleixner wrote:
> Sorry, let me clarify.  After this patch we have.
>
> typedef union irqentry_state {
> 	bool	exit_rcu;
> 	bool	lockdep;
> } irqentry_state_t;
>
> Which reflects the mutual exclusion of the 2 variables.

Huch? From the patch I gave you:

 #ifndef irqentry_state
 typedef struct irqentry_state {
 	bool    exit_rcu;
+       bool    lockdep;
 } irqentry_state_t;
 #endif

How is that a union?

> But then when the pkrs stuff is added the union changes back to a structure and
> looks like this.

So you want:

  1) Move stuff to struct irqentry_state (my patch)

  2) Change it to a union and pass it as pointer at the same time

  3) Change it back to struct to add PKRS

> Is that clear?

What's clear is that the above is nonsense. We can just do

 #ifndef irqentry_state
 typedef struct irqentry_state {
 	union {
         	bool    exit_rcu;
                bool    lockdep;
        };        
 } irqentry_state_t;
 #endif

right in the patch which I gave you. Because that actually makes sense.

Thanks,

        tglx