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[106.167.137.155]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-72aad8fd4e2sm16684872b3a.169.2024.12.28.16.17.19 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 28 Dec 2024 16:17:20 -0800 (PST) Message-ID: <24e3f1ee-ce06-44dc-a43f-64ec0a6f4c7b@gmail.com> Date: Sun, 29 Dec 2024 09:17:16 +0900 Precedence: bulk X-Mailing-List: perfbook@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3] CodeSamples: Work around removal of liburcu-signal To: =?UTF-8?Q?Leonardo_Br=C3=A1s?= , "Paul E. McKenney" Cc: perfbook@vger.kernel.org, Akira Yokosawa References: <672873fa-5e2a-4ef3-88ea-35e980305e2f@gmail.com> <3ba48d72c81ae3aaa6dbfc9bd44fd30f455cd157.camel@gmail.com> Content-Language: en-US From: Akira Yokosawa In-Reply-To: <3ba48d72c81ae3aaa6dbfc9bd44fd30f455cd157.camel@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Hi, Leonardo Brás wrote: [...] >> Hi Akira, >> >> That's a creative way of dealing with this issue, but if we want to add that >> complexity, I would rather use $(pkg-config --libs liburcu). >> >> Wouldn't this fix the issue as well? >> >> Thanks! > > Also, according to Paul's comment on v2 patch it shouldn't be needed: > >>> On the other hand, sys_membarrier() was introduced in 2015 (5b25b13ab08f6), >>> and no supported kernel (>v4.2) should still miss this syscall. Is it worth >>> the added complexity? Is so, let's do it. > >> If the -lurcu-signal is left off for old versions of the userspace RCU >> library, doesn't it simply fall back to using explicit memory barriers? >> Or am I yet again misremembering? > >> Thanx, Paul > > Isn't the above correct? > I have no idea ..., but your v2 patch causes this build error with liburcu <15.0: ------------------------------------------------------------------------ cc -g -O3 -Wall -fcommon -o route_rcu route_rcu.c ../lib/random.c -lpthread -lurcu /usr/bin/ld: /tmp/ccjHTQfN.o: warning: relocation against `urcu_signal_gp' in read-only section `.text' /usr/bin/ld: /tmp/ccjHTQfN.o: in function `_urcu_signal_read_lock': /usr/include/x86_64-linux-gnu/urcu/static/urcu-signal.h:97: undefined reference to `urcu_signal_reader' /usr/bin/ld: /tmp/ccjHTQfN.o: in function `_urcu_signal_read_lock_update': /usr/include/x86_64-linux-gnu/urcu/static/urcu-signal.h:75: undefined reference to `urcu_signal_gp' /usr/bin/ld: /tmp/ccjHTQfN.o: in function `urcu_common_wake_up_gp': /usr/include/x86_64-linux-gnu/urcu/static/urcu-common.h:96: undefined reference to `urcu_signal_gp' /usr/bin/ld: /usr/include/x86_64-linux-gnu/urcu/static/urcu-common.h:96: undefined reference to `urcu_signal_gp' /usr/bin/ld: /usr/include/x86_64-linux-gnu/urcu/static/urcu-common.h:97: undefined reference to `urcu_signal_gp' /usr/bin/ld: /tmp/ccjHTQfN.o: in function `futex': /usr/include/x86_64-linux-gnu/urcu/futex.h:72: undefined reference to `urcu_signal_gp' /usr/bin/ld: /tmp/ccjHTQfN.o:/usr/include/x86_64-linux-gnu/urcu/static/urcu-common.h:97: more undefined references to `urcu_signal_gp' follow /usr/bin/ld: /tmp/ccjHTQfN.o: in function `perftest_reader': git/perfbook/CodeSamples/defer/routetorture.h:103: undefined reference to `urcu_signal_register_thread' /usr/bin/ld: git/perfbook/CodeSamples/defer/routetorture.h:126: undefined reference to `urcu_signal_synchronize_rcu' /usr/bin/ld: git/perfbook/CodeSamples/defer/routetorture.h:128: undefined reference to `urcu_signal_synchronize_rcu' /usr/bin/ld: git/perfbook/CodeSamples/defer/routetorture.h:130: undefined reference to `urcu_signal_unregister_thread' /usr/bin/ld: /tmp/ccjHTQfN.o: in function `route_del': git/perfbook/CodeSamples/defer/route_rcu.c:124: undefined reference to `urcu_signal_call_rcu' /usr/bin/ld: /tmp/ccjHTQfN.o: in function `stresstest_updater': git/perfbook/CodeSamples/defer/routetorture.h:216: undefined reference to `urcu_signal_register_thread' /usr/bin/ld: git/perfbook/CodeSamples/defer/routetorture.h:260: undefined reference to `urcu_signal_synchronize_rcu' /usr/bin/ld: git/perfbook/CodeSamples/defer/routetorture.h:262: undefined reference to `urcu_signal_synchronize_rcu' /usr/bin/ld: git/perfbook/CodeSamples/defer/routetorture.h:264: undefined reference to `urcu_signal_unregister_thread' /usr/bin/ld: /tmp/ccjHTQfN.o: in function `route_clear': git/perfbook/CodeSamples/defer/route_rcu.c:149: undefined reference to `urcu_signal_synchronize_rcu' /usr/bin/ld: /tmp/ccjHTQfN.o: in function `smoketest': git/perfbook/CodeSamples/defer/routetorture.h:47: undefined reference to `urcu_signal_register_thread' /usr/bin/ld: git/perfbook/CodeSamples/defer/routetorture.h:62: undefined reference to `urcu_signal_unregister_thread' /usr/bin/ld: warning: creating DT_TEXTREL in a PIE collect2: error: ld returned 1 exit status make[1]: *** [Makefile:134: route_rcu] Error 1 make[1]: Leaving directory 'git/perfbook/CodeSamples/defer' ---------------------------------------------------------------- This is under Ubuntu 22.04 LTS. This looks to me as an unacceptable build regression. The use of $(pkg-config --libs liburcu) didn't occur to me. I'll give it a try. Thanks, Akira