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authorH.J. Lu <hjl.tools@gmail.com>2023-04-27 13:06:15 -0700
committerH.J. Lu <hjl.tools@gmail.com>2023-04-28 13:38:38 -0700
commita443bd3fb233186038b8b483959ecb7978d1abea (patch)
tree53948f90d590b84afe22a42ec49cc2ec2fe0c700
parenta225cb3ee9a22021312ae25c37595cd9d1995a1f (diff)
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__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.
-rw-r--r--sysdeps/unix/sysv/linux/Makefile2
-rw-r--r--sysdeps/unix/sysv/linux/check_pf.c15
2 files changed, 17 insertions, 0 deletions
diff --git a/sysdeps/unix/sysv/linux/Makefile b/sysdeps/unix/sysv/linux/Makefile
index aec7a94..0160be8 100644
--- a/sysdeps/unix/sysv/linux/Makefile
+++ b/sysdeps/unix/sysv/linux/Makefile
@@ -529,6 +529,8 @@ sysdep_headers += \
sysdep_routines += \
netlink_assert_response \
# sysdep_routines
+
+CFLAGS-check_pf.c += -fexceptions
endif
# Don't compile the ctype glue code, since there is no old non-GNU C library.
diff --git a/sysdeps/unix/sysv/linux/check_pf.c b/sysdeps/unix/sysv/linux/check_pf.c
index b157c51..2b0b8b6 100644
--- a/sysdeps/unix/sysv/linux/check_pf.c
+++ b/sysdeps/unix/sysv/linux/check_pf.c
@@ -292,6 +292,14 @@ make_request (int fd, pid_t pid)
return NULL;
}
+#ifdef __EXCEPTIONS
+static void
+cancel_handler (void *arg __attribute__((unused)))
+{
+ /* Release the lock. */
+ __libc_lock_unlock (lock);
+}
+#endif
void
attribute_hidden
@@ -304,6 +312,10 @@ __check_pf (bool *seen_ipv4, bool *seen_ipv6,
struct cached_data *olddata = NULL;
struct cached_data *data = NULL;
+#ifdef __EXCEPTIONS
+ /* Make sure that lock is released when the thread is cancelled. */
+ __libc_cleanup_push (cancel_handler, NULL);
+#endif
__libc_lock_lock (lock);
if (cache_valid_p ())
@@ -338,6 +350,9 @@ __check_pf (bool *seen_ipv4, bool *seen_ipv6,
}
}
+#ifdef __EXCEPTIONS
+ __libc_cleanup_pop (0);
+#endif
__libc_lock_unlock (lock);
if (data != NULL)