Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1672369

Re: [PATCH] rcu: remove unused variable in boot_cpu_state_init

Show all headers | View raw

* Paul E. McKenney <paulmck@linux.vnet.ibm.com> wrote:

> On Wed, Jun 21, 2017 at 11:57:28PM +0200, Arnd Bergmann wrote:
> > Without CONFIG_SMP, we get a harmless warning about
> > an unused variable:
> > 
> > kernel/cpu.c: In function 'boot_cpu_state_init':
> > kernel/cpu.c:1778:6: error: unused variable 'cpu' [-Werror=unused-variable]
> > 
> > This reworks the function to have the declaration inside
> > of the #ifdef.
> > 
> > Fixes: faeb334286b7 ("rcu: Migrate callbacks earlier in the CPU-offline timeline")
> > Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> 
> I simply added a __maybe_unused in 6441c656acde ("rcu: Migrate callbacks
> earlier in the CPU-offline timeline") in my -rcu tree.  However, your
> approach does have the advantage of complaining if the code using that
> variable is removed.
> 
> So, would you be OK with my folding your approach into my commit with
> attribution?

Also, note that __maybe_unused can be dangerous: it can hide a build warning where 
there's a _real_ unused variable bug now or due to future changes, causing a real 
runtime bug.

So I think we should consider it a syntactic construct to avoid.

Thanks,

	Ingo

Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

[PATCH] rcu: remove unused variable in boot_cpu_state_init Arnd Bergmann <arnd@arndb.de> - 2017-06-22 00:00 +0200
  Re: [PATCH] rcu: remove unused variable in boot_cpu_state_init "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-06-22 00:20 +0200
    Re: [PATCH] rcu: remove unused variable in boot_cpu_state_init Arnd Bergmann <arnd@arndb.de> - 2017-06-22 00:20 +0200
      Re: [PATCH] rcu: remove unused variable in boot_cpu_state_init "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-06-22 16:40 +0200
        Re: [PATCH] rcu: remove unused variable in boot_cpu_state_init "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-06-22 23:20 +0200
    Re: [PATCH] rcu: remove unused variable in boot_cpu_state_init Ingo Molnar <mingo@kernel.org> - 2017-06-22 09:30 +0200
      Re: [PATCH] rcu: remove unused variable in boot_cpu_state_init Arnd Bergmann <arnd@arndb.de> - 2017-06-22 09:50 +0200
        Re: [PATCH] rcu: remove unused variable in boot_cpu_state_init Ingo Molnar <mingo@kernel.org> - 2017-06-22 10:00 +0200
          Re: [PATCH] rcu: remove unused variable in boot_cpu_state_init Ingo Molnar <mingo@kernel.org> - 2017-06-22 10:00 +0200
            Re: [PATCH] rcu: remove unused variable in boot_cpu_state_init Ingo Molnar <mingo@kernel.org> - 2017-06-22 10:00 +0200
              Re: [PATCH] rcu: remove unused variable in boot_cpu_state_init Arnd Bergmann <arnd@arndb.de> - 2017-06-22 11:00 +0200
                Re: [PATCH] rcu: remove unused variable in boot_cpu_state_init Ingo Molnar <mingo@kernel.org> - 2017-06-22 11:10 +0200
                Re: [PATCH] rcu: remove unused variable in boot_cpu_state_init Arnd Bergmann <arnd@arndb.de> - 2017-06-22 11:50 +0200
      Re: [PATCH] rcu: remove unused variable in boot_cpu_state_init "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-06-22 17:00 +0200

csiph-web