This test case catches lost wake up introduced by commit 339ddb53d3
("fs/epoll: remove unnecessary wakeups of nested epoll")
The test is simple: we have 10 threads and 10 event fds. Each thread
can harvest only 1 event. 1 producer fires all 10 events at once and
waits that all 10 events will be observed by 10 threads.
In case of lost wakeup epoll_wait() will timeout and 0 will be returned.
Test case catches two sort of problems: forgotten wakeup on event, which
hits the ->ovflist list, this problem was fixed by:
5a2513239750 ("eventpoll: fix missing wakeup for ovflist in ep_poll_callback")
the other problem is when several sequential events hit the same waiting
thread, thus other waiters get no wakeups. Problem is fixed in the
following patch.
Signed-off-by: Roman Penyaev <rpenyaev@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Khazhismel Kumykov <khazhy@google.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Heiher <r@hev.cc>
Cc: Jason Baron <jbaron@akamai.com>
Link: http://lkml.kernel.org/r/20200430130326.1368509-1-rpenyaev@suse.de
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
epoll build fails to find pthread lib. Fix Makefile to use LDLIBS
instead of LDFLAGS. LDLIBS is the right flag to use here with -l
option when invoking ld.
gcc -I../../../../../usr/include/ -lpthread epoll_wakeup_test.c -o .../tools/testing/selftests/filesystems/epoll/epoll_wakeup_test
/usr/bin/ld: /tmp/ccaZvJUl.o: in function `kill_timeout':
epoll_wakeup_test.c:(.text+0x4dd): undefined reference to `pthread_kill'
/usr/bin/ld: epoll_wakeup_test.c:(.text+0x4f2): undefined reference to `pthread_kill'
/usr/bin/ld: /tmp/ccaZvJUl.o: in function `epoll9':
epoll_wakeup_test.c:(.text+0x6382): undefined reference to `pthread_create'
/usr/bin/ld: epoll_wakeup_test.c:(.text+0x64d2): undefined reference to `pthread_create'
/usr/bin/ld: epoll_wakeup_test.c:(.text+0x6626): undefined reference to `pthread_join'
/usr/bin/ld: epoll_wakeup_test.c:(.text+0x684c): undefined reference to `pthread_tryjoin_np'
/usr/bin/ld: epoll_wakeup_test.c:(.text+0x6864): undefined reference to `pthread_kill'
/usr/bin/ld: epoll_wakeup_test.c:(.text+0x6878): undefined reference to `pthread_join'
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
