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SubjectRe: [PATCH V2] rcu: change return type to bool
On Wed, May 27, 2015 at 08:56:25AM +0200, Nicholas Mc Guire wrote:
> Type-checking coccinelle spatches are being used to locate type mismatches
> between function signatures and return values in this case this produced:
> ./kernel/rcu/srcu.c:271 WARNING: return of wrong type
> int != unsigned long,
>
> srcu_readers_active() returns an int that is the sum of per_cpu unsigned
> long but the only user is cleanup_srcu_struct() which is using it as a
> boolean (condition) to see if there is any readers rather than actually
> using the approximate number of readers. The theoretically possible
> unsigned long overflow case does not need to be handled explicitly - if
> we had 4G++ readers then something else went wrong a long time ago.
>
> proposal: change the return type to boolean. The function name is left
> unchanged as it fits the naming expectation for a boolean.
>
> patch was compile tested for x86_64_defconfig (implies CONFIG_SRCU=y)
>
> patch is against 4.1-rc5 (localversion-next is -next-20150525)
>
> Signed-off-by: Nicholas Mc Guire <hofrat@osadl.org>

OK, I have queued this for testing. If Lai Jiangshan is OK with it,
I am OK with it.

Thanx, Paul

> ---
>
> V2: dropped the unnecessary !! conversion to boolean. for the details
> see Joe Perches <joe@perches.com> clarification at
> http://lkml.org/lkml/2015/5/24/47
>
> kernel/rcu/srcu.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/rcu/srcu.c b/kernel/rcu/srcu.c
> index fb33d35..de35087 100644
> --- a/kernel/rcu/srcu.c
> +++ b/kernel/rcu/srcu.c
> @@ -252,14 +252,15 @@ static bool srcu_readers_active_idx_check(struct srcu_struct *sp, int idx)
> }
>
> /**
> - * srcu_readers_active - returns approximate number of readers.
> + * srcu_readers_active - returns true if there are readers. and false
> + * otherwise
> * @sp: which srcu_struct to count active readers (holding srcu_read_lock).
> *
> * Note that this is not an atomic primitive, and can therefore suffer
> * severe errors when invoked on an active srcu_struct. That said, it
> * can be useful as an error check at cleanup time.
> */
> -static int srcu_readers_active(struct srcu_struct *sp)
> +static bool srcu_readers_active(struct srcu_struct *sp)
> {
> int cpu;
> unsigned long sum = 0;
> --
> 1.7.10.4
>



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