__check_pf: Add a cancellation cleanup handler [BZ #20975]

There are reports for hang in __check_pf:

https://github.com/JoeDog/siege/issues/4

It is reproducible only under specific configurations:

1. Large number of cores (>= 64) and large number of threads (> 3X of
the number of cores) with long lived socket connection.
2. Low power (frequency) mode.
3. Power management is enabled.

While holding lock, __check_pf calls make_request which calls __sendto
and __recvmsg.  Since __sendto and __recvmsg are cancellation points,
lock held by __check_pf won't be released and can cause deadlock when
thread cancellation happens in __sendto or __recvmsg.  Add a cancellation
cleanup handler for __check_pf to unlock the lock when cancelled by
another thread.  This fixes BZ #20975 and the siege hang issue.

(cherry picked from commit a443bd3fb233186038b8b483959ecb7978d1abea)

1 files changed, 2 insertions, 0 deletions

diff --git a/sysdeps/unix/sysv/linux/Makefile b/sysdeps/unix/sysv/linux/Makefile
index f298878e8f..94747b37a6 100644
--- a/sysdeps/unix/sysv/linux/Makefile
+++ b/sysdeps/unix/sysv/linux/Makefile
@@ -456,6 +456,8 @@ sysdep_headers += netinet/if_fddi.h netinet/if_tr.h \
 		  netrom/netrom.h netpacket/packet.h netrose/rose.h \
 		  neteconet/ec.h netiucv/iucv.h
 sysdep_routines += netlink_assert_response
+
+CFLAGS-check_pf.c += -fexceptions
 endif
 
 # Don't compile the ctype glue code, since there is no old non-GNU C library.