Since commit 31158ad02d ("rqspinlock: Add deadlock detection
and recovery") the updated path on re-entrancy now reports deadlock
via -EDEADLK instead of the previous -EBUSY.
Also, the way reentrancy was exercised (via fentry/lookup_elem_raw)
has been fragile because lookup_elem_raw may be inlined
(find_kernel_btf_id() will return -ESRCH).
To fix this fentry is attached to bpf_obj_free_fields() instead of
lookup_elem_raw() and:
- The htab map is made to use a BTF-described struct val with a
struct bpf_timer so that check_and_free_fields() reliably calls
bpf_obj_free_fields() on element replacement.
- The selftest is updated to do two updates to the same key (insert +
replace) in prog_test.
- The selftest is updated to align with expected errno with the
kernel’s current behavior.
Signed-off-by: Saket Kumar Bhaskar <skb99@linux.ibm.com>
Tested-by: Venkat Rao Bagalkote <venkat88@linux.ibm.com>
Link: https://lore.kernel.org/r/20251117060752.129648-1-skb99@linux.ibm.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
One test demonstrates the reentrancy of hash map update on the same
bucket should fail, and another one shows concureently updates of
the same hash map bucket should succeed and not fail due to
the reentrancy checking for bucket lock.
There is no trampoline support on s390x, so move htab_update to
denylist.
Signed-off-by: Hou Tao <houtao1@huawei.com>
Link: https://lore.kernel.org/r/20220831042629.130006-4-houtao@huaweicloud.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
