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Fix create_slab(): set memory pointer after marking it inaccessible #1260

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Fix create_slab(): set memory pointer after marking it inaccessible #1260

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@ldorau ldorau commented Apr 14, 2025 •
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Description

Fix create_slab() - set memory pointer after marking it inaccessible.

It is supposed to be a fix for the following data race:
https://github.com/ldorau/unified-memory-framework/actions/runs/14440708601/job/40490018121

WARNING: ThreadSanitizer: data race (pid=274219)
  Write of size 8 at 0x7f1a7201b268 by thread T10 (mutexes: write M0):
    #0 trackingAlloc /home/runner/work/unified-memory-framework/unified-memory-framework/src/provider/provider_tracking.c:474:11 (test_disjoint_pool+0x16375b) (BuildId: 5ab0ee73819682a89fed68fe86e9030a46e89243)
    #1 umfMemoryProviderAlloc /home/runner/work/unified-memory-framework/unified-memory-framework/src/memory_provider.c:245:9 (test_disjoint_pool+0x15ff4e) (BuildId: 5ab0ee73819682a89fed68fe86e9030a46e89243)
    #2 create_slab /home/runner/work/unified-memory-framework/unified-memory-framework/src/pool/pool_disjoint.c:116:11 (test_disjoint_pool+0x16ff06) (BuildId: 5ab0ee73819682a89fed68fe86e9030a46e89243)
    #3 bucket_create_slab /home/runner/work/unified-memory-framework/unified-memory-framework/src/pool/pool_disjoint.c:345:20 (test_disjoint_pool+0x16f5f8) (BuildId: 5ab0ee73819682a89fed68fe86e9030a46e89243)
    #4 bucket_get_avail_slab /home/runner/work/unified-memory-framework/unified-memory-framework/src/pool/pool_disjoint.c:368:9 (test_disjoint_pool+0x16f294) (BuildId: 5ab0ee73819682a89fed68fe86e9030a46e89243)
    #5 bucket_get_free_chunk /home/runner/work/unified-memory-framework/unified-memory-framework/src/pool/pool_disjoint.c:321:33 (test_disjoint_pool+0x16c6d5) (BuildId: 5ab0ee73819682a89fed68fe86e9030a46e89243)
    #6 disjoint_pool_aligned_malloc /home/runner/work/unified-memory-framework/unified-memory-framework/src/pool/pool_disjoint.c:763:11 (test_disjoint_pool+0x16c2a7) (BuildId: 5ab0ee73819682a89fed68fe86e9030a46e89243)
    #7 umfPoolAlignedMalloc /home/runner/work/unified-memory-framework/unified-memory-framework/src/memory_pool.c:195:12 (test_disjoint_pool+0x15f0a1) (BuildId: 5ab0ee73819682a89fed68fe86e9030a46e89243)
    #8 pow2AlignedAllocHelper(umf_memory_pool_t*) /home/runner/work/unified-memory-framework/unified-memory-framework/test/poolFixtures.hpp:216:25 (test_disjoint_pool+0xe6f40) (BuildId: 5ab0ee73819682a89fed68fe86e9030a46e89243)
    #9 umfPoolTest_multiThreadedpow2AlignedAlloc_Test::TestBody()::$_1::operator()(umf_memory_pool_t*) const /home/runner/work/unified-memory-framework/unified-memory-framework/test/poolFixtures.hpp:299:9 (test_disjoint_pool+0xfe801) (BuildId: 5ab0ee73819682a89fed68fe86e9030a46e89243)
    #10 void std::__invoke_impl<void, umfPoolTest_multiThreadedpow2AlignedAlloc_Test::TestBody()::$_1, umf_memory_pool_t*>(std::__invoke_other, umfPoolTest_multiThreadedpow2AlignedAlloc_Test::TestBody()::$_1&&, umf_memory_pool_t*&&) /usr/bin/../lib/gcc/x86_64-linux-gnu/12/../../../../include/c++/12/bits/invoke.h:61:14 (test_disjoint_pool+0xfe79a) (BuildId: 5ab0ee73819682a89fed68fe86e9030a46e89243)
    #11 std::__invoke_result<umfPoolTest_multiThreadedpow2AlignedAlloc_Test::TestBody()::$_1, umf_memory_pool_t*>::type std::__invoke<umfPoolTest_multiThreadedpow2AlignedAlloc_Test::TestBody()::$_1, umf_memory_pool_t*>(umfPoolTest_multiThreadedpow2AlignedAlloc_Test::TestBody()::$_1&&, umf_memory_pool_t*&&) /usr/bin/../lib/gcc/x86_64-linux-gnu/12/../../../../include/c++/12/bits/invoke.h:96:14 (test_disjoint_pool+0xfe66a) (BuildId: 5ab0ee73819682a89fed68fe86e9030a46e89243)
    #12 void std::thread::_Invoker<std::tuple<umfPoolTest_multiThreadedpow2AlignedAlloc_Test::TestBody()::$_1, umf_memory_pool_t*> >::_M_invoke<0ul, 1ul>(std::_Index_tuple<0ul, 1ul>) /usr/bin/../lib/gcc/x86_64-linux-gnu/12/../../../../include/c++/12/bits/std_thread.h:279:13 (test_disjoint_pool+0xfe5f2) (BuildId: 5ab0ee73819682a89fed68fe86e9030a46e89243)
    #13 std::thread::_Invoker<std::tuple<umfPoolTest_multiThreadedpow2AlignedAlloc_Test::TestBody()::$_1, umf_memory_pool_t*> >::operator()() /usr/bin/../lib/gcc/x86_64-linux-gnu/12/../../../../include/c++/12/bits/std_thread.h:286:11 (test_disjoint_pool+0xfe575) (BuildId: 5ab0ee73819682a89fed68fe86e9030a46e89243)
    #14 std::thread::_State_impl<std::thread::_Invoker<std::tuple<umfPoolTest_multiThreadedpow2AlignedAlloc_Test::TestBody()::$_1, umf_memory_pool_t*> > >::_M_run() /usr/bin/../lib/gcc/x86_64-linux-gnu/12/../../../../include/c++/12/bits/std_thread.h:231:13 (test_disjoint_pool+0xfe3c9) (BuildId: 5ab0ee73819682a89fed68fe86e9030a46e89243)
    #15 <null> <null> (libstdc++.so.6+0xdc252) (BuildId: e37fe1a879783838de78cbc8c80621fa685d58a2)

  Previous read of size 8 at 0x7f1a7201b268 by thread T7:
    #0 slab_get_end /home/runner/work/unified-memory-framework/unified-memory-framework/src/pool/pool_disjoint.c:179:38 (test_disjoint_pool+0x16cf99) (BuildId: 5ab0ee73819682a89fed68fe86e9030a46e89243)
    #1 disjoint_pool_free /home/runner/work/unified-memory-framework/unified-memory-framework/src/pool/pool_disjoint.c:843:32 (test_disjoint_pool+0x16d1c9) (BuildId: 5ab0ee73819682a89fed68fe86e9030a46e89243)
    #2 umfPoolFree /home/runner/work/unified-memory-framework/unified-memory-framework/src/memory_pool.c:215:12 (test_disjoint_pool+0x15eaa3) (BuildId: 5ab0ee73819682a89fed68fe86e9030a46e89243)
    #3 pow2AlignedAllocHelper(umf_memory_pool_t*) /home/runner/work/unified-memory-framework/unified-memory-framework/test/poolFixtures.hpp:224:39 (test_disjoint_pool+0xe73e2) (BuildId: 5ab0ee73819682a89fed68fe86e9030a46e89243)
    #4 umfPoolTest_multiThreadedpow2AlignedAlloc_Test::TestBody()::$_1::operator()(umf_memory_pool_t*) const /home/runner/work/unified-memory-framework/unified-memory-framework/test/poolFixtures.hpp:299:9 (test_disjoint_pool+0xfe801) (BuildId: 5ab0ee73819682a89fed68fe86e9030a46e89243)
    #5 void std::__invoke_impl<void, umfPoolTest_multiThreadedpow2AlignedAlloc_Test::TestBody()::$_1, umf_memory_pool_t*>(std::__invoke_other, umfPoolTest_multiThreadedpow2AlignedAlloc_Test::TestBody()::$_1&&, umf_memory_pool_t*&&) /usr/bin/../lib/gcc/x86_64-linux-gnu/12/../../../../include/c++/12/bits/invoke.h:61:14 (test_disjoint_pool+0xfe79a) (BuildId: 5ab0ee73819682a89fed68fe86e9030a46e89243)
    #6 std::__invoke_result<umfPoolTest_multiThreadedpow2AlignedAlloc_Test::TestBody()::$_1, umf_memory_pool_t*>::type std::__invoke<umfPoolTest_multiThreadedpow2AlignedAlloc_Test::TestBody()::$_1, umf_memory_pool_t*>(umfPoolTest_multiThreadedpow2AlignedAlloc_Test::TestBody()::$_1&&, umf_memory_pool_t*&&) /usr/bin/../lib/gcc/x86_64-linux-gnu/12/../../../../include/c++/12/bits/invoke.h:96:14 (test_disjoint_pool+0xfe66a) (BuildId: 5ab0ee73819682a89fed68fe86e9030a46e89243)
    #7 void std::thread::_Invoker<std::tuple<umfPoolTest_multiThreadedpow2AlignedAlloc_Test::TestBody()::$_1, umf_memory_pool_t*> >::_M_invoke<0ul, 1ul>(std::_Index_tuple<0ul, 1ul>) /usr/bin/../lib/gcc/x86_64-linux-gnu/12/../../../../include/c++/12/bits/std_thread.h:279:13 (test_disjoint_pool+0xfe5f2) (BuildId: 5ab0ee73819682a89fed68fe86e9030a46e89243)
    #8 std::thread::_Invoker<std::tuple<umfPoolTest_multiThreadedpow2AlignedAlloc_Test::TestBody()::$_1, umf_memory_pool_t*> >::operator()() /usr/bin/../lib/gcc/x86_64-linux-gnu/12/../../../../include/c++/12/bits/std_thread.h:286:11 (test_disjoint_pool+0xfe575) (BuildId: 5ab0ee73819682a89fed68fe86e9030a46e89243)
    #9 std::thread::_State_impl<std::thread::_Invoker<std::tuple<umfPoolTest_multiThreadedpow2AlignedAlloc_Test::TestBody()::$_1, umf_memory_pool_t*> > >::_M_run() /usr/bin/../lib/gcc/x86_64-linux-gnu/12/../../../../include/c++/12/bits/std_thread.h:231:13 (test_disjoint_pool+0xfe3c9) (BuildId: 5ab0ee73819682a89fed68fe86e9030a46e89243)
    #10 <null> <null> (libstdc++.so.6+0xdc252) (BuildId: e37fe1a879783838de78cbc8c80621fa685d58a2)

Checklist

  • Code compiles without errors locally
  • All tests pass locally
  • CI workflows execute properly

@ldorau ldorau requested a review from a team as a code owner April 14, 2025 11:13
@ldorau ldorau requested a review from bratpiorka April 14, 2025 11:18
bratpiorka
bratpiorka reviewed Apr 14, 2025
View reviewed changes
src/pool/pool_disjoint.c
utils_annotate_memory_inaccessible(slab->mem_ptr, slab->slab_size);
utils_annotate_memory_inaccessible(slab_mem_ptr, slab->slab_size);

utils_atomic_store_release_ptr(&slab->mem_ptr, slab_mem_ptr);
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@bratpiorka bratpiorka Apr 14, 2025

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I don't understand this fix. Should slab->mem_ptr always be accessed atomically? Why? This address isn't supposed to change during the lifetime of a slab.

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@ldorau ldorau Apr 14, 2025

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I have updated the description of this PR - you can find the full trace there:
It is supposed to be a fix for the following data race:
https://github.com/ldorau/unified-memory-framework/actions/runs/14440708601/job/40490018121

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@bratpiorka bratpiorka Apr 14, 2025

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I don't know how this could fix the problem. In the logs, I can see that thread T7 is reading a value from a slab that is not fully created yet. This is strange as the slab is registered later in pool_register_slab() AFTER the create_slab() finishes.

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@ldorau ldorau Apr 14, 2025

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OK, I will investigate it deeper

@ldorau ldorau marked this pull request as draft April 14, 2025 13:53
@ldorau ldorau closed this Apr 17, 2025
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