linux-kernel - Re: [PATCH] powerpc: silence a -Wcast-function-type warning in dawr_write_file

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Message-ID: <20190515131441.GA3072@infradead.org>
Date:   Wed, 15 May 2019 06:14:41 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Mathieu Malaterre <malat@...ian.org>
Cc:     Michael Ellerman <mpe@...erman.id.au>,
        Michael Neuling <mikey@...ling.org>,
        linux-kernel@...r.kernel.org, Paul Mackerras <paulus@...ba.org>,
        linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH] powerpc: silence a -Wcast-function-type warning in
 dawr_write_file_bool

On Wed, May 15, 2019 at 02:09:42PM +0200, Mathieu Malaterre wrote:
> In commit c1fe190c0672 ("powerpc: Add force enable of DAWR on P9
> option") the following piece of code was added:
> 
>    smp_call_function((smp_call_func_t)set_dawr, &null_brk, 0);
> 
> Since GCC 8 this trigger the following warning about incompatible
> function types:

And the warning is there for a reason, and should not be hidden
behind a cast.  This should instead be fixed by something like this:

diff --git a/arch/powerpc/kernel/hw_breakpoint.c b/arch/powerpc/kernel/hw_breakpoint.c
index da307dd93ee3..a26b67a1be83 100644
--- a/arch/powerpc/kernel/hw_breakpoint.c
+++ b/arch/powerpc/kernel/hw_breakpoint.c
@@ -384,6 +384,12 @@ void hw_breakpoint_pmu_read(struct perf_event *bp)
 bool dawr_force_enable;
 EXPORT_SYMBOL_GPL(dawr_force_enable);
 
+
+static void set_dawr_cb(void *info)
+{
+	set_dawr(info);
+}
+
 static ssize_t dawr_write_file_bool(struct file *file,
 				    const char __user *user_buf,
 				    size_t count, loff_t *ppos)
@@ -403,7 +409,7 @@ static ssize_t dawr_write_file_bool(struct file *file,
 
 	/* If we are clearing, make sure all CPUs have the DAWR cleared */
 	if (!dawr_force_enable)
-		smp_call_function((smp_call_func_t)set_dawr, &null_brk, 0);
+		smp_call_function(set_dawr_cb, &null_brk, 0);
 
 	return rc;
 }