tree 3e4ca03bb68728a490fca45c1e238b37d79cfed9
parent ded5d36f9cf50fdfbeb73301b2fdf4f707c5ce3a
author Arnaldo Carvalho de Melo <acme@redhat.com> 1579106793 -0300
committer Arnaldo Carvalho de Melo <acme@redhat.com> 1579106869 -0300

pahole: Make --contains look for more than just unions, structs

Look for typedefs, enums and types that descend from 'struct type', that
is:

  static inline int tag__is_type(const struct tag *tag)
  {
          return tag__is_union(tag)   ||
                 tag__is_struct(tag)  ||
                 tag__is_typedef(tag) ||
                 tag__is_rvalue_reference_type(tag) ||
                 tag__is_enumeration(tag);
  }

So now we can do more interesting queries, lets see, what are the data
structures that embed a raw spinlock in the linux kernel?

  $ pahole --contains raw_spinlock_t
  task_struct
  rw_semaphore
  hrtimer_cpu_base
  prev_cputime
  percpu_counter
  ratelimit_state
  perf_event_context
  task_delay_info
  perf_cpu_context
  perf_addr_filters_head
  fprop_local_percpu
  ld_semaphore
  er_account
  intel_excl_cntrs
  perf_amd_iommu
  irq_desc
  irq_chip_generic
  nmi_desc
  ssb_state
  semaphore
  uv_hub_nmi_s
  kretprobe
  swait_queue_head
  kvm_task_sleep_head
  kthread_worker
  root_domain
  cpudl
  rt_bandwidth
  dl_bandwidth
  dl_bw
  cfs_bandwidth
  rq
  rt_rq
  sugov_policy
  rt_mutex
  rcu_node
  rcu_data
  rcu_state
  timer_base
  cpu_stopper
  trace_array
  ring_buffer_per_cpu
  pcpu_freelist_head
  bpf_lru_list
  bpf_lru_locallist
  bucket
  lpm_trie
  bpf_queue_stack
  $

This is using the /sys/kernel/btf/vmlinux file, so it is really fast:

  $ time pahole --contains raw_spinlock_t > /dev/null

  real	0m0.034s
  user	0m0.023s
  sys	0m0.011s
  $

Look at one of those, say:

  $ pahole bpf_queue_stack
  struct bpf_queue_stack {
  	struct bpf_map             map;                  /*     0   256 */

  	/* XXX last struct has 40 bytes of padding */

  	/* --- cacheline 4 boundary (256 bytes) --- */
  	raw_spinlock_t             lock;                 /*   256     4 */
  	u32                        head;                 /*   260     4 */
  	u32                        tail;                 /*   264     4 */
  	u32                        size;                 /*   268     4 */
  	char                       elements[];           /*   272     0 */

  	/* size: 320, cachelines: 5, members: 6 */
  	/* padding: 48 */
  	/* paddings: 1, sum paddings: 40 */
  };
  $

But you may be intested only in RCU stuff, so...

  $ pahole --contains raw_spinlock_t --prefix rcu
  rcu_node
  rcu_data
  rcu_state
  $ pahole rcu_node,rcu_data,rcu_state | egrep '(^struct|raw_spinlock_t)'
  struct rcu_data {
  	raw_spinlock_t             nocb_lock;            /*   288     4 */
  	raw_spinlock_t             nocb_bypass_lock;     /*   384     4 */
  	raw_spinlock_t             nocb_gp_lock;         /*   448     4 */
  struct rcu_node {
  	raw_spinlock_t             lock;                 /*     0     4 */
  	raw_spinlock_t             fqslock;              /*   320     4 */
  struct rcu_state {
  	raw_spinlock_t             ofl_lock;             /*  3328     4 */
  $

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>