Hi James,
On 10/25/23 13:03, James Morse wrote:
> The resctrl CLOSID allocator uses a single 32bit word to track which
> CLOSID are free. The setting and clearing of bits is open coded.
>
> A subsequent patch adds closid_allocated(), which adds more open
> coded bitmaps operations. These will eventually need changing to use
> the bitops helpers so that a CLOSID bitmap of the correct size can be
> allocated dynamically.
>
> Convert the existing open coded bit manipulations of closid_free_map
> to use __set_bit() and friends. These don't need to be atomic as this
> list is protected by the mutex.
>
> Tested-by: Shaopeng Tan <tan.shaopeng@fujitsu.com>
> Tested-by: Peter Newman <peternewman@google.com>
> Reviewed-by: Shaopeng Tan <tan.shaopeng@fujitsu.com>
> Signed-off-by: James Morse <james.morse@arm.com>
Reviewed-by: Babu Moger <babu.moger@amd.com>
>
> ---
> Changes since v6:
> * Use the __ inatomic helpers and add lockdep_assert_held() annotations to
> document how this is safe.
> * Fixed a resctrl_closid_is_free()/closid_allocated() rename in the commit
> message.
> * Use RESCTRL_RESERVED_CLOSID to improve readability.
> ---
> arch/x86/kernel/cpu/resctrl/rdtgroup.c | 16 +++++++++++-----
> 1 file changed, 11 insertions(+), 5 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> index 9864cb49d58c..f6051a3e7262 100644
> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> @@ -111,7 +111,7 @@ void rdt_staged_configs_clear(void)
> * - Our choices on how to configure each resource become progressively more
> * limited as the number of resources grows.
> */
> -static int closid_free_map;
> +static unsigned long closid_free_map;
> static int closid_free_map_len;
>
> int closids_supported(void)
> @@ -131,7 +131,7 @@ static void closid_init(void)
> closid_free_map = BIT_MASK(rdt_min_closid) - 1;
>
> /* CLOSID 0 is always reserved for the default group */
> - closid_free_map &= ~1;
> + __clear_bit(RESCTRL_RESERVED_CLOSID, &closid_free_map);
> closid_free_map_len = rdt_min_closid;
> }
>
> @@ -139,17 +139,21 @@ static int closid_alloc(void)
> {
> u32 closid = ffs(closid_free_map);
>
> + lockdep_assert_held(&rdtgroup_mutex);
> +
> if (closid == 0)
> return -ENOSPC;
> closid--;
> - closid_free_map &= ~(1 << closid);
> + __clear_bit(closid, &closid_free_map);
>
> return closid;
> }
>
> void closid_free(int closid)
> {
> - closid_free_map |= 1 << closid;
> + lockdep_assert_held(&rdtgroup_mutex);
> +
> + __set_bit(closid, &closid_free_map);
> }
>
> /**
> @@ -161,7 +165,9 @@ void closid_free(int closid)
> */
> static bool closid_allocated(unsigned int closid)
> {
> - return (closid_free_map & (1 << closid)) == 0;
> + lockdep_assert_held(&rdtgroup_mutex);
> +
> + return !test_bit(closid, &closid_free_map);
> }
>
> /**
--
Thanks
Babu Moger