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authorMartin KaFai Lau <martin.lau@kernel.org>2024-10-23 16:47:51 -0700
committerAlexei Starovoitov <ast@kernel.org>2024-10-24 10:25:59 -0700
commit5bd5bab76669b1e1551f03f5fcbc165f3fa8d269 (patch)
tree742c3259a2dd2c833ab7954e0f17a0675a600035 /tools/perf/scripts/python/call-graph-from-postgresql.py
parentbpf: Add "bool swap_uptrs" arg to bpf_local_storage_update() and bpf_selem_alloc() (diff)
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bpf: Postpone bpf_selem_free() in bpf_selem_unlink_storage_nolock()
In a later patch, bpf_selem_free() will call unpin_user_page() through bpf_obj_free_fields(). unpin_user_page() may take spin_lock. However, some bpf_selem_free() call paths have held a raw_spin_lock. Like this: raw_spin_lock_irqsave() bpf_selem_unlink_storage_nolock() bpf_selem_free() unpin_user_page() spin_lock() To avoid spinlock nested in raw_spinlock, bpf_selem_free() should be done after releasing the raw_spinlock. The "bool reuse_now" arg is replaced with "struct hlist_head *free_selem_list" in bpf_selem_unlink_storage_nolock(). The bpf_selem_unlink_storage_nolock() will append the to-be-free selem at the free_selem_list. The caller of bpf_selem_unlink_storage_nolock() will need to call the new bpf_selem_free_list(free_selem_list, reuse_now) to free the selem after releasing the raw_spinlock. Note that the selem->snode cannot be reused for linking to the free_selem_list because the selem->snode is protected by the raw_spinlock that we want to avoid holding. A new "struct hlist_node free_node;" is union-ized with the rcu_head. Only the first one successfully hlist_del_init_rcu(&selem->snode) will be able to use the free_node. After succeeding hlist_del_init_rcu(&selem->snode), the free_node and rcu_head usage is serialized such that they can share the 16 bytes in a union. Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org> Link: https://lore.kernel.org/r/20241023234759.860539-5-martin.lau@linux.dev Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'tools/perf/scripts/python/call-graph-from-postgresql.py')
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