diff options
| author | Aboorva Devarajan <aboorvad@linux.ibm.com> | 2026-06-11 09:11:02 +0530 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2026-06-21 11:37:38 -0700 |
| commit | cea5702144615878600d3a39b5d8b3cc34719012 (patch) | |
| tree | 2c5a57140418ee9a161346583725d162e391391c /tools | |
| parent | 8edb0e769ce2a996774df83485781dd9f4bc2d44 (diff) | |
| download | ath-cea5702144615878600d3a39b5d8b3cc34719012.tar.gz | |
selftests/mm: fix exclusive_cow test fork() handling
The test ignores the return value of fork(), so both the parent and the
(newly created) child run the COW verification loops and then call
hmm_buffer_free() before returning into the kselftest harness, which
_exit()s each side. This duplicated teardown sequence has been observed
to manifest as a SIGSEGV in the test child, e.g.:
hmm-tests[360141]: segfault (11) at 0 nip 10006964 lr 1000ac3c code 1
in hmm-tests[6964,10000000+30000]
Fix this by adopting the same fork()-then-wait pattern already used by the
nearby anon_write_child / anon_write_child_shared tests in this file: the
child performs the COW verification and then _exit(0)s so it does not run
the test teardown, while the parent independently verifies COW, waits for
the child, and only then frees the buffer.
Link: https://lore.kernel.org/20260611034102.1030738-4-aboorvad@linux.ibm.com
Fixes: b659baea75469 ("mm: selftests for exclusive device memory")
Signed-off-by: Aboorva Devarajan <aboorvad@linux.ibm.com>
Cc: Alex Sierra <alex.sierra@amd.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Balbir Singh <balbirs@nvidia.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Leon Romanovsky <leon@kernel.org>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: Sayali Patil <sayalip@linux.ibm.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'tools')
| -rw-r--r-- | tools/testing/selftests/mm/hmm-tests.c | 31 |
1 files changed, 28 insertions, 3 deletions
diff --git a/tools/testing/selftests/mm/hmm-tests.c b/tools/testing/selftests/mm/hmm-tests.c index 8f4f824670436..e4c49699f3f72 100644 --- a/tools/testing/selftests/mm/hmm-tests.c +++ b/tools/testing/selftests/mm/hmm-tests.c @@ -1884,6 +1884,8 @@ TEST_F(hmm, exclusive_cow) unsigned long i; int *ptr; int ret; + pid_t pid; + int status; npages = ALIGN(HMM_BUFFER_SIZE, self->page_size) >> self->page_shift; ASSERT_NE(npages, 0); @@ -1912,14 +1914,37 @@ TEST_F(hmm, exclusive_cow) ASSERT_EQ(ret, 0); ASSERT_EQ(buffer->cpages, npages); - fork(); + pid = fork(); + if (pid == -1) + ASSERT_EQ(pid, 0); - /* Fault pages back to system memory and check them. */ + if (pid == 0) { + /* + * Child verifies COW independently, then _exit(0)s so it does + * not run the test teardown. A failed ASSERT_* here makes the + * harness abort() the child, so the parent sees + * !WIFEXITED(status) below and fails in turn. + */ + for (i = 0, ptr = buffer->ptr; i < size / sizeof(*ptr); ++i) + ASSERT_EQ(ptr[i]++, i); + + for (i = 0, ptr = buffer->ptr; i < size / sizeof(*ptr); ++i) + ASSERT_EQ(ptr[i], i + 1); + + _exit(0); + } + + /* Parent: also increment to verify COW works for both processes. */ for (i = 0, ptr = buffer->ptr; i < size / sizeof(*ptr); ++i) ASSERT_EQ(ptr[i]++, i); for (i = 0, ptr = buffer->ptr; i < size / sizeof(*ptr); ++i) - ASSERT_EQ(ptr[i], i+1); + ASSERT_EQ(ptr[i], i + 1); + + /* Parent: wait for child and then free the buffer. */ + ASSERT_EQ(waitpid(pid, &status, 0), pid); + ASSERT_TRUE(WIFEXITED(status)); + ASSERT_EQ(WEXITSTATUS(status), 0); hmm_buffer_free(buffer); } |