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    Subject[PATCH 5.19 1022/1157] x86/numa: Use cpumask_available instead of hardcoded NULL check
    Date
    From: Siddh Raman Pant <code@siddh.me>

    [ Upstream commit 625395c4a0f4775e0fe00f616888d2e6c1ba49db ]

    GCC-12 started triggering a new warning:

    arch/x86/mm/numa.c: In function ‘cpumask_of_node’:
    arch/x86/mm/numa.c:916:39: warning: the comparison will always evaluate as ‘false’ for the address of ‘node_to_cpumask_map’ will never be NULL [-Waddress]
    916 | if (node_to_cpumask_map[node] == NULL) {
    | ^~

    node_to_cpumask_map is of type cpumask_var_t[].

    When CONFIG_CPUMASK_OFFSTACK is set, cpumask_var_t is typedef'd to a
    pointer for dynamic allocation, else to an array of one element. The
    "wicked game" can be checked on line 700 of include/linux/cpumask.h.

    The original code in debug_cpumask_set_cpu() and cpumask_of_node() were
    probably written by the original authors with CONFIG_CPUMASK_OFFSTACK=y
    (i.e. dynamic allocation) in mind, checking if the cpumask was available
    via a direct NULL check.

    When CONFIG_CPUMASK_OFFSTACK is not set, GCC gives the above warning
    while compiling the kernel.

    Fix that by using cpumask_available(), which does the NULL check when
    CONFIG_CPUMASK_OFFSTACK is set, otherwise returns true. Use it wherever
    such checks are made.

    Conditional definitions of cpumask_available() can be found along with
    the definition of cpumask_var_t. Check the cpumask.h reference mentioned
    above.

    Fixes: c032ef60d1aa ("cpumask: convert node_to_cpumask_map[] to cpumask_var_t")
    Fixes: de2d9445f162 ("x86: Unify node_to_cpumask_map handling between 32 and 64bit")
    Signed-off-by: Siddh Raman Pant <code@siddh.me>
    Signed-off-by: Ingo Molnar <mingo@kernel.org>
    Link: https://lore.kernel.org/r/20220731160913.632092-1-code@siddh.me
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    arch/x86/mm/numa.c | 4 ++--
    1 file changed, 2 insertions(+), 2 deletions(-)

    diff --git a/arch/x86/mm/numa.c b/arch/x86/mm/numa.c
    index e8b061557887..2aadb2019b4f 100644
    --- a/arch/x86/mm/numa.c
    +++ b/arch/x86/mm/numa.c
    @@ -867,7 +867,7 @@ void debug_cpumask_set_cpu(int cpu, int node, bool enable)
    return;
    }
    mask = node_to_cpumask_map[node];
    - if (!mask) {
    + if (!cpumask_available(mask)) {
    pr_err("node_to_cpumask_map[%i] NULL\n", node);
    dump_stack();
    return;
    @@ -913,7 +913,7 @@ const struct cpumask *cpumask_of_node(int node)
    dump_stack();
    return cpu_none_mask;
    }
    - if (node_to_cpumask_map[node] == NULL) {
    + if (!cpumask_available(node_to_cpumask_map[node])) {
    printk(KERN_WARNING
    "cpumask_of_node(%d): no node_to_cpumask_map!\n",
    node);
    --
    2.35.1


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