From mboxrd@z Thu Jan 1 00:00:00 1970 From: hewenliang4@huawei.com (hewenliang (C)) Date: Thu, 19 Sep 2019 01:58:25 +0000 Subject: [lttng-dev] =?utf-8?b?562U5aSNOiBbUkZDIFBBVENIIHVyY3VdIEZpeDog?= =?utf-8?q?rculfhash_worker_needs_to_unblock_to_SIGRCU?= In-Reply-To: <58194404.12563.1568818629781.JavaMail.zimbra@efficios.com> References: <20190917153403.9143-1-mathieu.desnoyers@efficios.com> <4dea6ba2125a419a9d158bce40a91eb7@huawei.com> <58194404.12563.1568818629781.JavaMail.zimbra@efficios.com> Message-ID: Dear Mathieu, Thank you so much. -----Original Message----- From: Mathieu Desnoyers [mailto:mathieu.desnoyers@efficios.com] Sent: Wednesday, September 18, 2019 10:57 PM To: hewenliang (C) Cc: linfeilong ; lttng-dev ; Paul E . McKenney Subject: Re: [lttng-dev] ??: [RFC PATCH urcu] Fix: rculfhash worker needs to unblock to SIGRCU ----- On Sep 17, 2019, at 11:32 PM, h00486469 hewenliang4 at huawei.com wrote: > Dear Mathieu, > > The patch that you have modified has the similar logic with mine. I > have tested the patch and it also fixes the problem. > By the way, would you please add me as the co-author just as below, > thank you so much. Of course, no problem! Process-wise, I will use the Linux kernel's Documentation/process/submitting-patches.rst "Co-developed-by:". I will change the patch to name you as the main author (From: field), and add myself to a "Co-developed-by:" like this: From: hewenliang Signed-off-by: hewenliang Co-developed-by: Mathieu Desnoyers Signed-off-by: Mathieu Desnoyers Cc: Paul E. McKenney I don't think the "Reported-by" is useful given that you are the original author. It seems to properly capture contributions. Thanks! Mathieu > > Reported-by: hewenliang > Signed-off-by: Mathieu Desnoyers > Signed-off-by: hewenliang > Cc: Paul E. McKenney > > Thanks > > > ----- Original Message ----- > From: Mathieu Desnoyers [mailto:mathieu.desnoyers@efficios.com] > Sent: September 17, 2019 23:34 > hewenliang (C) > Cc: lttng-dev at lists.lttng.org; Mathieu Desnoyers > ; Paul E . McKenney > > Subject: [RFC PATCH urcu] Fix: rculfhash worker needs to unblock to SIGRCU > > In urcu-signal flavor, call_rcu_thread calls synchronize_rcu which > will send SIGRCU signal to all registed threads, and then loops to > wait need_mb to be cleared. However, the registed workqueue_thread > does not process the SIGRCU signal, and never clear the need_mb. > Based on above, call_rcu_thread and workqueue_thread will wait forever > for completion of the grace period: call_rcu_thread which holds the > rcu_registry_lock, waits for workqueue_thread to do cmm_smp_mb. > While workqueue thread never does cmm_smp_mb because of signal > blocking, and it will eventually wait to get rcu_registry_lock in do_resize_cb. > > The phenomenon is as follows, which is easy to be triggered: > > (gdb) t 2 > [Switching to thread 2 (Thread 0xffff83c3b080 (LWP 27116))] > 0 0x0000ffff845296c4 in poll () from /lib64/libc.so.6 > (gdb) bt > 0 0x0000ffff845296c4 in poll () from /lib64/libc.so.6 > 1 0x0000ffff8461b93c in force_mb_all_readers () at urcu.c:241 > 2 0x0000ffff8461c748 in smp_mb_master () at urcu.c:249 > 3 urcu_signal_synchronize_rcu () at urcu.c:445 > 4 0x0000ffff8461d004 in call_rcu_thread at urcu-call-rcu-impl.h:364 > 5 0x0000ffff845eb8bc in start_thread () from /lib64/libpthread.so.0 > 6 0x0000ffff845335cc in thread_start () from /lib64/libc.so.6 > (gdb) t 3 > [Switching to thread 3 (Thread 0xffff8443c080 (LWP 27191))] > 0 0x0000ffff845f51c4 in __lll_lock_wait () from /lib64/libpthread.so.0 > (gdb) bt > 0 0x0000ffff845f51c4 in __lll_lock_wait () from /lib64/libpthread.so.0 > 1 0x0000ffff845ee048 in pthread_mutex_lock () from > /lib64/libpthread.so.0 > 2 0x0000ffff8461b814 in mutex_lock ( ) at > urcu.c:157 > 3 0x0000ffff8461b9e4 in urcu_signal_unregister_thread () at urcu.c:564 > 4 0x0000ffff8463e62c in do_resize_cb (work=0x11e2e790) at > rculfhash.c:2042 > 5 0x0000ffff8463c940 in workqueue_thread (arg=0x11e1d260) at > workqueue.c:228 > 6 0x0000ffff845eb8bc in start_thread () from /lib64/libpthread.so.0 > 7 0x0000ffff845335cc in thread_start () from /lib64/libc.so.6 > > So we should not block SIGRCU in workqueue thread to avoid blocking > forever in the grace period awaiting on the worker thread when using > urcu-signal flavor. > > Reported-by: hewenliang > Signed-off-by: Mathieu Desnoyers > Cc: Paul E. McKenney > Cc: hewenliang > --- > include/Makefile.am | 3 ++- > include/urcu/static/urcu-signal-nr.h | 42 ++++++++++++++++++++++++++++++++++++ > include/urcu/static/urcu-signal.h | 14 +----------- > src/rculfhash.c | 13 ++++++++--- > 4 files changed, 55 insertions(+), 17 deletions(-) create mode 100644 > include/urcu/static/urcu-signal-nr.h > > diff --git a/include/Makefile.am b/include/Makefile.am index > 34812d4..8f83641 100644 > --- a/include/Makefile.am > +++ b/include/Makefile.am > @@ -14,7 +14,8 @@ nobase_dist_include_HEADERS = urcu/compiler.h > urcu/hlist.h urcu/list.h \ > urcu/static/urcu-qsbr.h urcu/static/wfcqueue.h \ > urcu/static/wfqueue.h urcu/static/wfstack.h \ > urcu/static/urcu-mb.h urcu/static/urcu-memb.h \ > - urcu/static/urcu-signal.h urcu/static/urcu-common.h \ > + urcu/static/urcu-signal.h urcu/static/urcu-signal-nr.h \ > + urcu/static/urcu-common.h \ > urcu/tls-compat.h urcu/debug.h urcu/urcu.h urcu/urcu-bp.h \ > urcu/call-rcu.h urcu/defer.h \ > urcu/pointer.h urcu/urcu-qsbr.h urcu/flavor.h \ diff --git > a/include/urcu/static/urcu-signal-nr.h > b/include/urcu/static/urcu-signal-nr.h > new file mode 100644 > index 0000000..a488f3a > --- /dev/null > +++ b/include/urcu/static/urcu-signal-nr.h > @@ -0,0 +1,42 @@ > +#ifndef _STATIC_URCU_SIGNAL_NR_H > +#define _STATIC_URCU_SIGNAL_NR_H > + > +/* > + * static/urcu-signal-nr.h > + * > + * Userspace RCU header. > + * > + * Copyright (c) 2009 Mathieu Desnoyers > + > + * Copyright (c) 2009 Paul E. McKenney, IBM Corporation. > + * > + * This library is free software; you can redistribute it and/or > + * modify it under the terms of the GNU Lesser General Public > + * License as published by the Free Software Foundation; either > + * version 2.1 of the License, or (at your option) any later version. > + * > + * This library is distributed in the hope that it will be useful, > + * but WITHOUT ANY WARRANTY; without even the implied warranty of > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU > + * Lesser General Public License for more details. > + * > + * You should have received a copy of the GNU Lesser General Public > + * License along with this library; if not, write to the Free > +Software > + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA > +02110-1301 USA > + * > + * IBM's contributions to this file may be relicensed under LGPLv2 or later. > + */ > + > +/* > + * The signal number used by the RCU library can be overridden with > + * -DSIGRCU= when compiling the library. > + * Provide backward compatibility for liburcu 0.3.x SIGURCU. > + */ > +#ifdef SIGURCU > +#define SIGRCU SIGURCU > +#endif > + > +#ifndef SIGRCU > +#define SIGRCU SIGUSR1 > +#endif > + > +#endif /* _STATIC_URCU_SIGNAL_NR_H */ > diff --git a/include/urcu/static/urcu-signal.h > b/include/urcu/static/urcu-signal.h > index 385e6f5..f0faf3a 100644 > --- a/include/urcu/static/urcu-signal.h > +++ b/include/urcu/static/urcu-signal.h > @@ -44,6 +44,7 @@ > #include > #include > #include > +#include > > #ifdef __cplusplus > extern "C" { > @@ -57,19 +58,6 @@ extern "C" { > * This is required to permit relinking with newer versions of the library. > */ > > -/* > - * The signal number used by the RCU library can be overridden with > - * -DSIGRCU= when compiling the library. > - * Provide backward compatibility for liburcu 0.3.x SIGURCU. > - */ > -#ifdef SIGURCU > -#define SIGRCU SIGURCU > -#endif > - > -#ifndef SIGRCU > -#define SIGRCU SIGUSR1 > -#endif > - > extern struct urcu_gp urcu_signal_gp; > > extern DECLARE_URCU_TLS(struct urcu_reader, urcu_signal_reader); diff > --git a/src/rculfhash.c b/src/rculfhash.c index ff42df0..5b3c06b > 100644 > --- a/src/rculfhash.c > +++ b/src/rculfhash.c > @@ -273,6 +273,7 @@ > #include > #include > #include > +#include > #include > #include > #include > @@ -2151,18 +2152,24 @@ static struct urcu_atfork cds_lfht_atfork = { > .after_fork_child = cds_lfht_after_fork_child, }; > > -/* Block all signals to ensure we don't disturb the application. */ > +/* > + * Block all signals for the workqueue worker thread to ensure we > +don't > + * disturb the application. The SIGRCU signal needs to be unblocked > +for > + * the urcu-signal flavor. > + */ > static void cds_lfht_worker_init(struct urcu_workqueue *workqueue, > void *priv) > { > int ret; > sigset_t mask; > > - /* Block signal for entire process, so only our thread processes it. */ > ret = sigfillset(&mask); > if (ret) > urcu_die(errno); > - ret = pthread_sigmask(SIG_BLOCK, &mask, NULL); > + ret = sigdelset(&mask, SIGRCU); > + if (ret) > + urcu_die(ret); > + ret = pthread_sigmask(SIG_SETMASK, &mask, NULL); > if (ret) > urcu_die(ret); > } > -- > 2.11.0 > > _______________________________________________ > lttng-dev mailing list > lttng-dev at lists.lttng.org > https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com