On Mon, Jul 04, 2022 at 05:05:10PM +0200, Marco Elver wrote:
quoted hunk ↗ jump to hunk
+bool percpu_is_read_locked(struct percpu_rw_semaphore *sem)
+{
+ return per_cpu_sum(*sem->read_count) != 0;
+}
+EXPORT_SYMBOL_GPL(percpu_is_read_locked);
I don't think this is correct; read_count can have spurious increments.
If we look at __percpu_down_read_trylock(), it does roughly something
like this:
this_cpu_inc(*sem->read_count);
smp_mb();
if (!sem->block)
return true;
this_cpu_dec(*sem->read_count);
return false;
So percpu_is_read_locked() needs to ensure the read_count is non-zero
*and* that block is not set.
That said; I really dislike the whole _is_locked family with a passion.
Let me try and figure out what you need this for.