| Message ID | 20231005163922.87568-3-leitao@debian.org (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | New selftest for mm | expand |
On Thu, 2023-10-05 at 09:39 -0700, Breno Leitao wrote: > Create a selftest that exercises the race between page faults and > madvise(MADV_DONTNEED) in the same huge page. Do it by running two > threads that touches the huge page and madvise(MADV_DONTNEED) at the > same > time. > > ---------------------------------- > ./run_vmtests.sh: line 186: 595563 Bus error (core dumped) "$@" > [FAIL] > > This selftest goes together with the fix of the bug[1] itself. > > [1] > https://lore.kernel.org/all/20231001005659.2185316-1-riel@surriel.com/#r > > Signed-off-by: Breno Leitao <leitao@debian.org> Tested-and-reviewed-by: Rik van Riel <riel@surriel.com>
Hi Breno, On 05/10/2023 17:39, Breno Leitao wrote: > Create a selftest that exercises the race between page faults and > madvise(MADV_DONTNEED) in the same huge page. Do it by running two > threads that touches the huge page and madvise(MADV_DONTNEED) at the same > time. > > In case of a SIGBUS coming at pagefault, the test should fail, since we > hit the bug. > > The test doesn't have a signal handler, and if it fails, it fails like > the following > > ---------------------------------- > running ./hugetlb_fault_after_madv > ---------------------------------- > ./run_vmtests.sh: line 186: 595563 Bus error (core dumped) "$@" > [FAIL] > > This selftest goes together with the fix of the bug[1] itself. > > [1] https://lore.kernel.org/all/20231001005659.2185316-1-riel@surriel.com/#r > > Signed-off-by: Breno Leitao <leitao@debian.org> > --- > tools/testing/selftests/mm/Makefile | 1 + > .../selftests/mm/hugetlb_fault_after_madv.c | 73 +++++++++++++++++++ > tools/testing/selftests/mm/run_vmtests.sh | 4 + > 3 files changed, 78 insertions(+) > create mode 100644 tools/testing/selftests/mm/hugetlb_fault_after_madv.c > > diff --git a/tools/testing/selftests/mm/Makefile b/tools/testing/selftests/mm/Makefile > index 6a9fc5693145..e71ec9910c62 100644 > --- a/tools/testing/selftests/mm/Makefile > +++ b/tools/testing/selftests/mm/Makefile > @@ -68,6 +68,7 @@ TEST_GEN_FILES += split_huge_page_test > TEST_GEN_FILES += ksm_tests > TEST_GEN_FILES += ksm_functional_tests > TEST_GEN_FILES += mdwe_test > +TEST_GEN_FILES += hugetlb_fault_after_madv > > ifneq ($(ARCH),arm64) > TEST_GEN_PROGS += soft-dirty > diff --git a/tools/testing/selftests/mm/hugetlb_fault_after_madv.c b/tools/testing/selftests/mm/hugetlb_fault_after_madv.c > new file mode 100644 > index 000000000000..73b81c632366 > --- /dev/null > +++ b/tools/testing/selftests/mm/hugetlb_fault_after_madv.c > @@ -0,0 +1,73 @@ > +// SPDX-License-Identifier: GPL-2.0 > +#include <pthread.h> > +#include <stdio.h> > +#include <stdlib.h> > +#include <sys/mman.h> > +#include <sys/types.h> > +#include <unistd.h> > + > +#include "vm_util.h" > +#include "../kselftest.h" > + > +#define MMAP_SIZE (1 << 21) > +#define INLOOP_ITER 100 > + > +char *huge_ptr; > + > +/* Touch the memory while it is being madvised() */ > +void *touch(void *unused) > +{ > + char *ptr = (char *)huge_ptr; > + > + for (int i = 0; i < INLOOP_ITER; i++) > + ptr[0] = '.'; > + > + return NULL; > +} > + > +void *madv(void *unused) > +{ > + usleep(rand() % 10); > + > + for (int i = 0; i < INLOOP_ITER; i++) > + madvise(huge_ptr, MMAP_SIZE, MADV_DONTNEED); > + > + return NULL; > +} > + > +int main(void) > +{ > + unsigned long free_hugepages; > + pthread_t thread1, thread2; > + /* > + * On kernel 6.4, we are able to reproduce the problem with ~1000 > + * interactions > + */ > + int max = 10000; > + > + srand(getpid()); > + > + free_hugepages = get_free_hugepages(); > + if (free_hugepages != 1) { > + ksft_exit_skip("This test needs one and only one page to execute. Got %lu\n", > + free_hugepages); > + } > + > + while (max--) { > + huge_ptr = mmap(NULL, MMAP_SIZE, PROT_READ | PROT_WRITE, > + MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB, > + -1, 0); > + > + if ((unsigned long)huge_ptr == -1) > + ksft_exit_skip("Failed to allocated huge page\n"); > + > + pthread_create(&thread1, NULL, madv, NULL); > + pthread_create(&thread2, NULL, touch, NULL); > + > + pthread_join(thread1, NULL); > + pthread_join(thread2, NULL); > + munmap(huge_ptr, MMAP_SIZE); > + } > + > + return KSFT_PASS; > +} > diff --git a/tools/testing/selftests/mm/run_vmtests.sh b/tools/testing/selftests/mm/run_vmtests.sh > index 3e2bc818d566..9f53f7318a38 100755 > --- a/tools/testing/selftests/mm/run_vmtests.sh > +++ b/tools/testing/selftests/mm/run_vmtests.sh > @@ -221,6 +221,10 @@ CATEGORY="hugetlb" run_test ./hugepage-mremap > CATEGORY="hugetlb" run_test ./hugepage-vmemmap > CATEGORY="hugetlb" run_test ./hugetlb-madvise > > +# For this test, we need one and just one huge page > +echo 1 > /proc/sys/vm/nr_hugepages I've noticed that this change breaks some of the uffd-stress tests further down the file, because you have freed previously reserved hugepages that the test requires to run. I notice that the patch is already in mm-stable, so perhaps its possible to submit a patch that does a save and restore? Although I'm not sure if that might be tricky because the previous reservation is per-size and per-node (our CI does this on the kernel command line), and I suspect if you want just 1 huge page in the entire system you won't be able to get back to the previous state by just restoring this value? These are the failing tests for reference: # ------------------------------------ # running ./uffd-stress hugetlb 128 32 # ------------------------------------ # nr_pages: 64, nr_pages_per_cpu: 8 # ERROR: context init failed (errno=12, @uffd-stress.c:254) # [FAIL] # -------------------------------------------- # running ./uffd-stress hugetlb-private 128 32 # -------------------------------------------- # nr_pages: 64, nr_pages_per_cpu: 8 # ERROR: context init failed (errno=12, @uffd-stress.c:254) # [FAIL] Thanks, Ryan > +CATEGORY="hugetlb" run_test ./hugetlb_fault_after_madv > + > if test_selected "hugetlb"; then > echo "NOTE: These hugetlb tests provide minimal coverage. Use" > echo " https://github.com/libhugetlbfs/libhugetlbfs.git for"
On 02/11/2023 12:24, Ryan Roberts wrote: > Hi Breno, > > > On 05/10/2023 17:39, Breno Leitao wrote: >> Create a selftest that exercises the race between page faults and >> madvise(MADV_DONTNEED) in the same huge page. Do it by running two >> threads that touches the huge page and madvise(MADV_DONTNEED) at the same >> time. >> >> In case of a SIGBUS coming at pagefault, the test should fail, since we >> hit the bug. >> >> The test doesn't have a signal handler, and if it fails, it fails like >> the following >> >> ---------------------------------- >> running ./hugetlb_fault_after_madv >> ---------------------------------- >> ./run_vmtests.sh: line 186: 595563 Bus error (core dumped) "$@" >> [FAIL] >> >> This selftest goes together with the fix of the bug[1] itself. >> >> [1] https://lore.kernel.org/all/20231001005659.2185316-1-riel@surriel.com/#r >> >> Signed-off-by: Breno Leitao <leitao@debian.org> >> --- >> tools/testing/selftests/mm/Makefile | 1 + >> .../selftests/mm/hugetlb_fault_after_madv.c | 73 +++++++++++++++++++ >> tools/testing/selftests/mm/run_vmtests.sh | 4 + >> 3 files changed, 78 insertions(+) >> create mode 100644 tools/testing/selftests/mm/hugetlb_fault_after_madv.c >> >> diff --git a/tools/testing/selftests/mm/Makefile b/tools/testing/selftests/mm/Makefile >> index 6a9fc5693145..e71ec9910c62 100644 >> --- a/tools/testing/selftests/mm/Makefile >> +++ b/tools/testing/selftests/mm/Makefile >> @@ -68,6 +68,7 @@ TEST_GEN_FILES += split_huge_page_test >> TEST_GEN_FILES += ksm_tests >> TEST_GEN_FILES += ksm_functional_tests >> TEST_GEN_FILES += mdwe_test >> +TEST_GEN_FILES += hugetlb_fault_after_madv >> >> ifneq ($(ARCH),arm64) >> TEST_GEN_PROGS += soft-dirty >> diff --git a/tools/testing/selftests/mm/hugetlb_fault_after_madv.c b/tools/testing/selftests/mm/hugetlb_fault_after_madv.c >> new file mode 100644 >> index 000000000000..73b81c632366 >> --- /dev/null >> +++ b/tools/testing/selftests/mm/hugetlb_fault_after_madv.c >> @@ -0,0 +1,73 @@ >> +// SPDX-License-Identifier: GPL-2.0 >> +#include <pthread.h> >> +#include <stdio.h> >> +#include <stdlib.h> >> +#include <sys/mman.h> >> +#include <sys/types.h> >> +#include <unistd.h> >> + >> +#include "vm_util.h" >> +#include "../kselftest.h" >> + >> +#define MMAP_SIZE (1 << 21) >> +#define INLOOP_ITER 100 >> + >> +char *huge_ptr; >> + >> +/* Touch the memory while it is being madvised() */ >> +void *touch(void *unused) >> +{ >> + char *ptr = (char *)huge_ptr; >> + >> + for (int i = 0; i < INLOOP_ITER; i++) >> + ptr[0] = '.'; >> + >> + return NULL; >> +} >> + >> +void *madv(void *unused) >> +{ >> + usleep(rand() % 10); >> + >> + for (int i = 0; i < INLOOP_ITER; i++) >> + madvise(huge_ptr, MMAP_SIZE, MADV_DONTNEED); >> + >> + return NULL; >> +} >> + >> +int main(void) >> +{ >> + unsigned long free_hugepages; >> + pthread_t thread1, thread2; >> + /* >> + * On kernel 6.4, we are able to reproduce the problem with ~1000 >> + * interactions >> + */ >> + int max = 10000; >> + >> + srand(getpid()); >> + >> + free_hugepages = get_free_hugepages(); >> + if (free_hugepages != 1) { >> + ksft_exit_skip("This test needs one and only one page to execute. Got %lu\n", >> + free_hugepages); >> + } >> + >> + while (max--) { >> + huge_ptr = mmap(NULL, MMAP_SIZE, PROT_READ | PROT_WRITE, >> + MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB, >> + -1, 0); >> + >> + if ((unsigned long)huge_ptr == -1) >> + ksft_exit_skip("Failed to allocated huge page\n"); >> + >> + pthread_create(&thread1, NULL, madv, NULL); >> + pthread_create(&thread2, NULL, touch, NULL); >> + >> + pthread_join(thread1, NULL); >> + pthread_join(thread2, NULL); >> + munmap(huge_ptr, MMAP_SIZE); >> + } >> + >> + return KSFT_PASS; >> +} >> diff --git a/tools/testing/selftests/mm/run_vmtests.sh b/tools/testing/selftests/mm/run_vmtests.sh >> index 3e2bc818d566..9f53f7318a38 100755 >> --- a/tools/testing/selftests/mm/run_vmtests.sh >> +++ b/tools/testing/selftests/mm/run_vmtests.sh >> @@ -221,6 +221,10 @@ CATEGORY="hugetlb" run_test ./hugepage-mremap >> CATEGORY="hugetlb" run_test ./hugepage-vmemmap >> CATEGORY="hugetlb" run_test ./hugetlb-madvise >> >> +# For this test, we need one and just one huge page >> +echo 1 > /proc/sys/vm/nr_hugepages > > I've noticed that this change breaks some of the uffd-stress tests further down > the file, because you have freed previously reserved hugepages that the test > requires to run. I notice that the patch is already in mm-stable, so perhaps its > possible to submit a patch that does a save and restore? > > Although I'm not sure if that might be tricky because the previous reservation > is per-size and per-node (our CI does this on the kernel command line), and I > suspect if you want just 1 huge page in the entire system you won't be able to > get back to the previous state by just restoring this value? Actually on closer inspection, I don't think this will be a problem; simply saving and restoring the value around the test will be sufficient. I also notice that the binary for the new test is not added to the .gitignore, which is a minor annoyance. Thanks, Ryan > > These are the failing tests for reference: > > # ------------------------------------ > # running ./uffd-stress hugetlb 128 32 > # ------------------------------------ > # nr_pages: 64, nr_pages_per_cpu: 8 > # ERROR: context init failed (errno=12, @uffd-stress.c:254) > # [FAIL] > # -------------------------------------------- > # running ./uffd-stress hugetlb-private 128 32 > # -------------------------------------------- > # nr_pages: 64, nr_pages_per_cpu: 8 > # ERROR: context init failed (errno=12, @uffd-stress.c:254) > # [FAIL] > > Thanks, > Ryan > > > >> +CATEGORY="hugetlb" run_test ./hugetlb_fault_after_madv >> + >> if test_selected "hugetlb"; then >> echo "NOTE: These hugetlb tests provide minimal coverage. Use" >> echo " https://github.com/libhugetlbfs/libhugetlbfs.git for" >
Hello Ryan, On Thu, Nov 02, 2023 at 12:29:54PM +0000, Ryan Roberts wrote: > On 02/11/2023 12:24, Ryan Roberts wrote: > > On 05/10/2023 17:39, Breno Leitao wrote: > >> Create a selftest that exercises the race between page faults and > >> madvise(MADV_DONTNEED) in the same huge page. Do it by running two > >> threads that touches the huge page and madvise(MADV_DONTNEED) at the same > >> time. > >> > >> In case of a SIGBUS coming at pagefault, the test should fail, since we > >> hit the bug. > >> > >> The test doesn't have a signal handler, and if it fails, it fails like > >> the following > >> > >> ---------------------------------- > >> running ./hugetlb_fault_after_madv > >> ---------------------------------- > >> ./run_vmtests.sh: line 186: 595563 Bus error (core dumped) "$@" > >> [FAIL] > >> > >> This selftest goes together with the fix of the bug[1] itself. > >> > >> [1] https://lore.kernel.org/all/20231001005659.2185316-1-riel@surriel.com/#r > >> > >> Signed-off-by: Breno Leitao <leitao@debian.org> > >> --- > >> tools/testing/selftests/mm/Makefile | 1 + > >> .../selftests/mm/hugetlb_fault_after_madv.c | 73 +++++++++++++++++++ > >> tools/testing/selftests/mm/run_vmtests.sh | 4 + > >> 3 files changed, 78 insertions(+) > >> create mode 100644 tools/testing/selftests/mm/hugetlb_fault_after_madv.c > >> > >> diff --git a/tools/testing/selftests/mm/Makefile b/tools/testing/selftests/mm/Makefile > >> index 6a9fc5693145..e71ec9910c62 100644 > >> --- a/tools/testing/selftests/mm/Makefile > >> +++ b/tools/testing/selftests/mm/Makefile > >> @@ -68,6 +68,7 @@ TEST_GEN_FILES += split_huge_page_test > >> TEST_GEN_FILES += ksm_tests > >> TEST_GEN_FILES += ksm_functional_tests > >> TEST_GEN_FILES += mdwe_test > >> +TEST_GEN_FILES += hugetlb_fault_after_madv > >> > >> ifneq ($(ARCH),arm64) > >> TEST_GEN_PROGS += soft-dirty > >> diff --git a/tools/testing/selftests/mm/hugetlb_fault_after_madv.c b/tools/testing/selftests/mm/hugetlb_fault_after_madv.c > >> new file mode 100644 > >> index 000000000000..73b81c632366 > >> --- /dev/null > >> +++ b/tools/testing/selftests/mm/hugetlb_fault_after_madv.c > >> @@ -0,0 +1,73 @@ > >> +// SPDX-License-Identifier: GPL-2.0 > >> +#include <pthread.h> > >> +#include <stdio.h> > >> +#include <stdlib.h> > >> +#include <sys/mman.h> > >> +#include <sys/types.h> > >> +#include <unistd.h> > >> + > >> +#include "vm_util.h" > >> +#include "../kselftest.h" > >> + > >> +#define MMAP_SIZE (1 << 21) > >> +#define INLOOP_ITER 100 > >> + > >> +char *huge_ptr; > >> + > >> +/* Touch the memory while it is being madvised() */ > >> +void *touch(void *unused) > >> +{ > >> + char *ptr = (char *)huge_ptr; > >> + > >> + for (int i = 0; i < INLOOP_ITER; i++) > >> + ptr[0] = '.'; > >> + > >> + return NULL; > >> +} > >> + > >> +void *madv(void *unused) > >> +{ > >> + usleep(rand() % 10); > >> + > >> + for (int i = 0; i < INLOOP_ITER; i++) > >> + madvise(huge_ptr, MMAP_SIZE, MADV_DONTNEED); > >> + > >> + return NULL; > >> +} > >> + > >> +int main(void) > >> +{ > >> + unsigned long free_hugepages; > >> + pthread_t thread1, thread2; > >> + /* > >> + * On kernel 6.4, we are able to reproduce the problem with ~1000 > >> + * interactions > >> + */ > >> + int max = 10000; > >> + > >> + srand(getpid()); > >> + > >> + free_hugepages = get_free_hugepages(); > >> + if (free_hugepages != 1) { > >> + ksft_exit_skip("This test needs one and only one page to execute. Got %lu\n", > >> + free_hugepages); > >> + } > >> + > >> + while (max--) { > >> + huge_ptr = mmap(NULL, MMAP_SIZE, PROT_READ | PROT_WRITE, > >> + MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB, > >> + -1, 0); > >> + > >> + if ((unsigned long)huge_ptr == -1) > >> + ksft_exit_skip("Failed to allocated huge page\n"); > >> + > >> + pthread_create(&thread1, NULL, madv, NULL); > >> + pthread_create(&thread2, NULL, touch, NULL); > >> + > >> + pthread_join(thread1, NULL); > >> + pthread_join(thread2, NULL); > >> + munmap(huge_ptr, MMAP_SIZE); > >> + } > >> + > >> + return KSFT_PASS; > >> +} > >> diff --git a/tools/testing/selftests/mm/run_vmtests.sh b/tools/testing/selftests/mm/run_vmtests.sh > >> index 3e2bc818d566..9f53f7318a38 100755 > >> --- a/tools/testing/selftests/mm/run_vmtests.sh > >> +++ b/tools/testing/selftests/mm/run_vmtests.sh > >> @@ -221,6 +221,10 @@ CATEGORY="hugetlb" run_test ./hugepage-mremap > >> CATEGORY="hugetlb" run_test ./hugepage-vmemmap > >> CATEGORY="hugetlb" run_test ./hugetlb-madvise > >> > >> +# For this test, we need one and just one huge page > >> +echo 1 > /proc/sys/vm/nr_hugepages > > > > I've noticed that this change breaks some of the uffd-stress tests further down > > the file, because you have freed previously reserved hugepages that the test > > requires to run. I notice that the patch is already in mm-stable, so perhaps its > > possible to submit a patch that does a save and restore? > > > > Although I'm not sure if that might be tricky because the previous reservation > > is per-size and per-node (our CI does this on the kernel command line), and I > > suspect if you want just 1 huge page in the entire system you won't be able to > > get back to the previous state by just restoring this value? > > Actually on closer inspection, I don't think this will be a problem; simply > saving and restoring the value around the test will be sufficient. Thanks for checking it, I will prepare a patch that will restore the number of huge pages allocated after the test. > I also notice that the binary for the new test is not added to the .gitignore, > which is a minor annoyance. I will add the file to .gitignore also. Thanks for the heads-up.
On 03/11/2023 13:59, Breno Leitao wrote: > Hello Ryan, > > On Thu, Nov 02, 2023 at 12:29:54PM +0000, Ryan Roberts wrote: >> On 02/11/2023 12:24, Ryan Roberts wrote: >>> On 05/10/2023 17:39, Breno Leitao wrote: >>>> Create a selftest that exercises the race between page faults and >>>> madvise(MADV_DONTNEED) in the same huge page. Do it by running two >>>> threads that touches the huge page and madvise(MADV_DONTNEED) at the same >>>> time. >>>> >>>> In case of a SIGBUS coming at pagefault, the test should fail, since we >>>> hit the bug. >>>> >>>> The test doesn't have a signal handler, and if it fails, it fails like >>>> the following >>>> >>>> ---------------------------------- >>>> running ./hugetlb_fault_after_madv >>>> ---------------------------------- >>>> ./run_vmtests.sh: line 186: 595563 Bus error (core dumped) "$@" >>>> [FAIL] >>>> >>>> This selftest goes together with the fix of the bug[1] itself. >>>> >>>> [1] https://lore.kernel.org/all/20231001005659.2185316-1-riel@surriel.com/#r >>>> >>>> Signed-off-by: Breno Leitao <leitao@debian.org> >>>> --- >>>> tools/testing/selftests/mm/Makefile | 1 + >>>> .../selftests/mm/hugetlb_fault_after_madv.c | 73 +++++++++++++++++++ >>>> tools/testing/selftests/mm/run_vmtests.sh | 4 + >>>> 3 files changed, 78 insertions(+) >>>> create mode 100644 tools/testing/selftests/mm/hugetlb_fault_after_madv.c >>>> >>>> diff --git a/tools/testing/selftests/mm/Makefile b/tools/testing/selftests/mm/Makefile >>>> index 6a9fc5693145..e71ec9910c62 100644 >>>> --- a/tools/testing/selftests/mm/Makefile >>>> +++ b/tools/testing/selftests/mm/Makefile >>>> @@ -68,6 +68,7 @@ TEST_GEN_FILES += split_huge_page_test >>>> TEST_GEN_FILES += ksm_tests >>>> TEST_GEN_FILES += ksm_functional_tests >>>> TEST_GEN_FILES += mdwe_test >>>> +TEST_GEN_FILES += hugetlb_fault_after_madv >>>> >>>> ifneq ($(ARCH),arm64) >>>> TEST_GEN_PROGS += soft-dirty >>>> diff --git a/tools/testing/selftests/mm/hugetlb_fault_after_madv.c b/tools/testing/selftests/mm/hugetlb_fault_after_madv.c >>>> new file mode 100644 >>>> index 000000000000..73b81c632366 >>>> --- /dev/null >>>> +++ b/tools/testing/selftests/mm/hugetlb_fault_after_madv.c >>>> @@ -0,0 +1,73 @@ >>>> +// SPDX-License-Identifier: GPL-2.0 >>>> +#include <pthread.h> >>>> +#include <stdio.h> >>>> +#include <stdlib.h> >>>> +#include <sys/mman.h> >>>> +#include <sys/types.h> >>>> +#include <unistd.h> >>>> + >>>> +#include "vm_util.h" >>>> +#include "../kselftest.h" >>>> + >>>> +#define MMAP_SIZE (1 << 21) >>>> +#define INLOOP_ITER 100 >>>> + >>>> +char *huge_ptr; >>>> + >>>> +/* Touch the memory while it is being madvised() */ >>>> +void *touch(void *unused) >>>> +{ >>>> + char *ptr = (char *)huge_ptr; >>>> + >>>> + for (int i = 0; i < INLOOP_ITER; i++) >>>> + ptr[0] = '.'; >>>> + >>>> + return NULL; >>>> +} >>>> + >>>> +void *madv(void *unused) >>>> +{ >>>> + usleep(rand() % 10); >>>> + >>>> + for (int i = 0; i < INLOOP_ITER; i++) >>>> + madvise(huge_ptr, MMAP_SIZE, MADV_DONTNEED); >>>> + >>>> + return NULL; >>>> +} >>>> + >>>> +int main(void) >>>> +{ >>>> + unsigned long free_hugepages; >>>> + pthread_t thread1, thread2; >>>> + /* >>>> + * On kernel 6.4, we are able to reproduce the problem with ~1000 >>>> + * interactions >>>> + */ >>>> + int max = 10000; >>>> + >>>> + srand(getpid()); >>>> + >>>> + free_hugepages = get_free_hugepages(); >>>> + if (free_hugepages != 1) { >>>> + ksft_exit_skip("This test needs one and only one page to execute. Got %lu\n", >>>> + free_hugepages); >>>> + } >>>> + >>>> + while (max--) { >>>> + huge_ptr = mmap(NULL, MMAP_SIZE, PROT_READ | PROT_WRITE, >>>> + MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB, >>>> + -1, 0); >>>> + >>>> + if ((unsigned long)huge_ptr == -1) >>>> + ksft_exit_skip("Failed to allocated huge page\n"); >>>> + >>>> + pthread_create(&thread1, NULL, madv, NULL); >>>> + pthread_create(&thread2, NULL, touch, NULL); >>>> + >>>> + pthread_join(thread1, NULL); >>>> + pthread_join(thread2, NULL); >>>> + munmap(huge_ptr, MMAP_SIZE); >>>> + } >>>> + >>>> + return KSFT_PASS; >>>> +} >>>> diff --git a/tools/testing/selftests/mm/run_vmtests.sh b/tools/testing/selftests/mm/run_vmtests.sh >>>> index 3e2bc818d566..9f53f7318a38 100755 >>>> --- a/tools/testing/selftests/mm/run_vmtests.sh >>>> +++ b/tools/testing/selftests/mm/run_vmtests.sh >>>> @@ -221,6 +221,10 @@ CATEGORY="hugetlb" run_test ./hugepage-mremap >>>> CATEGORY="hugetlb" run_test ./hugepage-vmemmap >>>> CATEGORY="hugetlb" run_test ./hugetlb-madvise >>>> >>>> +# For this test, we need one and just one huge page >>>> +echo 1 > /proc/sys/vm/nr_hugepages >>> >>> I've noticed that this change breaks some of the uffd-stress tests further down >>> the file, because you have freed previously reserved hugepages that the test >>> requires to run. I notice that the patch is already in mm-stable, so perhaps its >>> possible to submit a patch that does a save and restore? >>> >>> Although I'm not sure if that might be tricky because the previous reservation >>> is per-size and per-node (our CI does this on the kernel command line), and I >>> suspect if you want just 1 huge page in the entire system you won't be able to >>> get back to the previous state by just restoring this value? >> >> Actually on closer inspection, I don't think this will be a problem; simply >> saving and restoring the value around the test will be sufficient. > > Thanks for checking it, I will prepare a patch that will restore the number > of huge pages allocated after the test. > >> I also notice that the binary for the new test is not added to the .gitignore, >> which is a minor annoyance. > > I will add the file to .gitignore also. Excellent - thanks! > > Thanks for the heads-up.
diff --git a/tools/testing/selftests/mm/Makefile b/tools/testing/selftests/mm/Makefile index 6a9fc5693145..e71ec9910c62 100644 --- a/tools/testing/selftests/mm/Makefile +++ b/tools/testing/selftests/mm/Makefile @@ -68,6 +68,7 @@ TEST_GEN_FILES += split_huge_page_test TEST_GEN_FILES += ksm_tests TEST_GEN_FILES += ksm_functional_tests TEST_GEN_FILES += mdwe_test +TEST_GEN_FILES += hugetlb_fault_after_madv ifneq ($(ARCH),arm64) TEST_GEN_PROGS += soft-dirty diff --git a/tools/testing/selftests/mm/hugetlb_fault_after_madv.c b/tools/testing/selftests/mm/hugetlb_fault_after_madv.c new file mode 100644 index 000000000000..73b81c632366 --- /dev/null +++ b/tools/testing/selftests/mm/hugetlb_fault_after_madv.c @@ -0,0 +1,73 @@ +// SPDX-License-Identifier: GPL-2.0 +#include <pthread.h> +#include <stdio.h> +#include <stdlib.h> +#include <sys/mman.h> +#include <sys/types.h> +#include <unistd.h> + +#include "vm_util.h" +#include "../kselftest.h" + +#define MMAP_SIZE (1 << 21) +#define INLOOP_ITER 100 + +char *huge_ptr; + +/* Touch the memory while it is being madvised() */ +void *touch(void *unused) +{ + char *ptr = (char *)huge_ptr; + + for (int i = 0; i < INLOOP_ITER; i++) + ptr[0] = '.'; + + return NULL; +} + +void *madv(void *unused) +{ + usleep(rand() % 10); + + for (int i = 0; i < INLOOP_ITER; i++) + madvise(huge_ptr, MMAP_SIZE, MADV_DONTNEED); + + return NULL; +} + +int main(void) +{ + unsigned long free_hugepages; + pthread_t thread1, thread2; + /* + * On kernel 6.4, we are able to reproduce the problem with ~1000 + * interactions + */ + int max = 10000; + + srand(getpid()); + + free_hugepages = get_free_hugepages(); + if (free_hugepages != 1) { + ksft_exit_skip("This test needs one and only one page to execute. Got %lu\n", + free_hugepages); + } + + while (max--) { + huge_ptr = mmap(NULL, MMAP_SIZE, PROT_READ | PROT_WRITE, + MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB, + -1, 0); + + if ((unsigned long)huge_ptr == -1) + ksft_exit_skip("Failed to allocated huge page\n"); + + pthread_create(&thread1, NULL, madv, NULL); + pthread_create(&thread2, NULL, touch, NULL); + + pthread_join(thread1, NULL); + pthread_join(thread2, NULL); + munmap(huge_ptr, MMAP_SIZE); + } + + return KSFT_PASS; +} diff --git a/tools/testing/selftests/mm/run_vmtests.sh b/tools/testing/selftests/mm/run_vmtests.sh index 3e2bc818d566..9f53f7318a38 100755 --- a/tools/testing/selftests/mm/run_vmtests.sh +++ b/tools/testing/selftests/mm/run_vmtests.sh @@ -221,6 +221,10 @@ CATEGORY="hugetlb" run_test ./hugepage-mremap CATEGORY="hugetlb" run_test ./hugepage-vmemmap CATEGORY="hugetlb" run_test ./hugetlb-madvise +# For this test, we need one and just one huge page +echo 1 > /proc/sys/vm/nr_hugepages +CATEGORY="hugetlb" run_test ./hugetlb_fault_after_madv + if test_selected "hugetlb"; then echo "NOTE: These hugetlb tests provide minimal coverage. Use" echo " https://github.com/libhugetlbfs/libhugetlbfs.git for"
Create a selftest that exercises the race between page faults and madvise(MADV_DONTNEED) in the same huge page. Do it by running two threads that touches the huge page and madvise(MADV_DONTNEED) at the same time. In case of a SIGBUS coming at pagefault, the test should fail, since we hit the bug. The test doesn't have a signal handler, and if it fails, it fails like the following ---------------------------------- running ./hugetlb_fault_after_madv ---------------------------------- ./run_vmtests.sh: line 186: 595563 Bus error (core dumped) "$@" [FAIL] This selftest goes together with the fix of the bug[1] itself. [1] https://lore.kernel.org/all/20231001005659.2185316-1-riel@surriel.com/#r Signed-off-by: Breno Leitao <leitao@debian.org> --- tools/testing/selftests/mm/Makefile | 1 + .../selftests/mm/hugetlb_fault_after_madv.c | 73 +++++++++++++++++++ tools/testing/selftests/mm/run_vmtests.sh | 4 + 3 files changed, 78 insertions(+) create mode 100644 tools/testing/selftests/mm/hugetlb_fault_after_madv.c