diff options
| author | Carlos O'Donell <carlos@redhat.com> | 2019-01-21 22:50:12 -0500 |
|---|---|---|
| committer | Carlos O'Donell <carlos@redhat.com> | 2019-01-31 20:47:55 -0500 |
| commit | 5fc9ed4c4058bfbdf51ad6e7aac7d209b580e8c4 (patch) | |
| tree | 5787bb93e87e93b3191c1d1d8e1bf61f5a99d3c2 /nptl/Makefile | |
| parent | 932329a5134665bfad601a8709da2602d943fc38 (diff) | |
| download | glibc-5fc9ed4c4058bfbdf51ad6e7aac7d209b580e8c4.tar glibc-5fc9ed4c4058bfbdf51ad6e7aac7d209b580e8c4.tar.gz glibc-5fc9ed4c4058bfbdf51ad6e7aac7d209b580e8c4.tar.bz2 glibc-5fc9ed4c4058bfbdf51ad6e7aac7d209b580e8c4.zip | |
nptl: Fix pthread_rwlock_try*lock stalls (Bug 23844)
For a full analysis of both the pthread_rwlock_tryrdlock() stall
and the pthread_rwlock_trywrlock() stall see:
https://sourceware.org/bugzilla/show_bug.cgi?id=23844#c14
In the pthread_rwlock_trydlock() function we fail to inspect for
PTHREAD_RWLOCK_FUTEX_USED in __wrphase_futex and wake the waiting
readers.
In the pthread_rwlock_trywrlock() function we write 1 to
__wrphase_futex and loose the setting of the PTHREAD_RWLOCK_FUTEX_USED
bit, again failing to wake waiting readers during unlock.
The fix in the case of pthread_rwlock_trydlock() is to check for
PTHREAD_RWLOCK_FUTEX_USED and wake the readers.
The fix in the case of pthread_rwlock_trywrlock() is to only write
1 to __wrphase_futex if we installed the write phase, since all other
readers would be spinning waiting for this step.
We add two new tests, one exercises the stall for
pthread_rwlock_trywrlock() which is easy to exercise, and one exercises
the stall for pthread_rwlock_trydlock() which is harder to exercise.
The pthread_rwlock_trywrlock() test fails consistently without the fix,
and passes after. The pthread_rwlock_tryrdlock() test fails roughly
5-10% of the time without the fix, and passes all the time after.
Signed-off-by: Carlos O'Donell <carlos@redhat.com>
Signed-off-by: Torvald Riegel <triegel@redhat.com>
Signed-off-by: Rik Prohaska <prohaska7@gmail.com>
Co-authored-by: Torvald Riegel <triegel@redhat.com>
Co-authored-by: Rik Prohaska <prohaska7@gmail.com>
Diffstat (limited to 'nptl/Makefile')
| -rw-r--r-- | nptl/Makefile | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/nptl/Makefile b/nptl/Makefile index 340282c6cb..0e316edfac 100644 --- a/nptl/Makefile +++ b/nptl/Makefile @@ -319,7 +319,8 @@ tests = tst-attr1 tst-attr2 tst-attr3 tst-default-attr \ tst-cnd-basic tst-mtx-trylock tst-cnd-broadcast \ tst-cnd-timedwait tst-thrd-detach tst-mtx-basic tst-thrd-sleep \ tst-mtx-recursive tst-tss-basic tst-call-once tst-mtx-timedlock \ - tst-rwlock-pwn + tst-rwlock-pwn \ + tst-rwlock-tryrdlock-stall tst-rwlock-trywrlock-stall tests-internal := tst-rwlock19 tst-rwlock20 \ tst-sem11 tst-sem12 tst-sem13 \ |