Quoting S.Çağlar Onur ([email protected]): > While testing https://github.com/lxc/lxc/pull/106, I found that concurrent > starts > are hanging time to time. I then reproduced the same problem in master and > got following; > > [caglar@oOo:~] sudo gdb -p 16221 > (gdb) bt > #0 __lll_lock_wait () at > ../nptl/sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:135 > #1 0x00007f495526515c in _L_lock_982 () from > /lib/x86_64-linux-gnu/libpthread.so.0 > #2 0x00007f4955264fab in __GI___pthread_mutex_lock (mutex=0x7f49556d4600 > <static_mutex>) at pthread_mutex_lock.c:64 > #3 0x00007f49554b27a6 in lock_mutex (l=l@entry=0x7f49556d4600 > <static_mutex>) at lxclock.c:78 > #4 0x00007f49554b2dac in static_lock () at lxclock.c:330 > #5 0x00007f4955498f71 in lxc_global_config_value > (option_name=option_name@entry=0x7f49554c02cf "cgroup.use") at utils.c:273 > #6 0x00007f495549926c in default_cgroup_use () at utils.c:366 > #7 0x00007f49554953bd in lxc_cgroup_load_meta () at cgroup.c:94 > #8 0x00007f495548debc in lxc_spawn (handler=handler@entry=0x7f49200af300) > at start.c:783 > #9 0x00007f495548e7a7 in __lxc_start (name=name@entry=0x7f49200b48a0 > "lxc-test-concurrent-4", conf=conf@entry=0x7f49200b2030, > ops=ops@entry=0x7f49556d3900 <start_ops>, data=data@entry=0x7f495487db90, > lxcpath=lxcpath@entry=0x7f49200b2010 "/var/lib/lxc") at start.c:951 > #10 0x00007f495548eb9c in lxc_start (name=0x7f49200b48a0 > "lxc-test-concurrent-4", argv=argv@entry=0x7f495487dbe0, > conf=conf@entry=0x7f49200b2030, lxcpath=0x7f49200b2010 "/var/lib/lxc") at > start.c:1048 > #11 0x00007f49554b68f1 in lxcapi_start (c=0x7f49200b1dd0, useinit=<optimized > out>, argv=0x7f495487dbe0) at lxccontainer.c:648 > #12 0x0000000000401317 in do_function (arguments=0x1aa80b0) at > concurrent.c:94 > #13 0x0000000000401499 in concurrent (arguments=<optimized out>) at > concurrent.c:130 > #14 0x00007f4955262f6e in start_thread (arg=0x7f495487e700) at > pthread_create.c:311 > #15 0x00007f4954f8d9cd in clone () at > ../sysdeps/unix/sysv/linux/x86_64/clone.S:113 > > It looks like both parent and child end up with locked mutex thus deadlocks. > > I ended up placing values in the thread local storage pool, instead of doing > "unlock the lock in the child" dance > > Signed-off-by: S.Çağlar Onur <[email protected]>
only question is, does this work in bionic? So long as it does, Acked-by: Serge E. Hallyn <[email protected]> > --- > src/lxc/lxclock.c | 13 ------------- > src/lxc/lxclock.h | 10 ---------- > src/lxc/utils.c | 16 +++------------- > 3 files changed, 3 insertions(+), 36 deletions(-) > > diff --git a/src/lxc/lxclock.c b/src/lxc/lxclock.c > index 64823d2..62e774f 100644 > --- a/src/lxc/lxclock.c > +++ b/src/lxc/lxclock.c > @@ -44,7 +44,6 @@ lxc_log_define(lxc_lock, lxc); > > #ifdef MUTEX_DEBUGGING > pthread_mutex_t thread_mutex = PTHREAD_ERRORCHECK_MUTEX_INITIALIZER_NP; > -pthread_mutex_t static_mutex = PTHREAD_ERRORCHECK_MUTEX_INITIALIZER_NP; > > inline void dump_stacktrace(void) > { > @@ -66,7 +65,6 @@ inline void dump_stacktrace(void) > } > #else > pthread_mutex_t thread_mutex = PTHREAD_MUTEX_INITIALIZER; > -pthread_mutex_t static_mutex = PTHREAD_MUTEX_INITIALIZER; > > inline void dump_stacktrace(void) {;} > #endif > @@ -324,17 +322,6 @@ void process_unlock(void) > unlock_mutex(&thread_mutex); > } > > -/* Protects static const values inside the lxc_global_config_value funtion */ > -void static_lock(void) > -{ > - lock_mutex(&static_mutex); > -} > - > -void static_unlock(void) > -{ > - unlock_mutex(&static_mutex); > -} > - > int container_mem_lock(struct lxc_container *c) > { > return lxclock(c->privlock, 0); > diff --git a/src/lxc/lxclock.h b/src/lxc/lxclock.h > index 820e819..a02a032 100644 > --- a/src/lxc/lxclock.h > +++ b/src/lxc/lxclock.h > @@ -123,16 +123,6 @@ extern void process_lock(void); > */ > extern void process_unlock(void); > > -/*! > - * \brief Lock global data. > - */ > -extern void static_lock(void); > - > -/*! > - * \brief Unlock global data. > - */ > -extern void static_unlock(void); > - > struct lxc_container; > > /*! > diff --git a/src/lxc/utils.c b/src/lxc/utils.c > index b605307..785f3e6 100644 > --- a/src/lxc/utils.c > +++ b/src/lxc/utils.c > @@ -253,8 +253,8 @@ const char *lxc_global_config_value(const char > *option_name) > { "cgroup.use", NULL }, > { NULL, NULL }, > }; > - /* Protected by a mutex to eliminate conflicting load and store > operations */ > - static const char *values[sizeof(options) / sizeof(options[0])] = { 0 }; > + /* placed in the thread local storage pool */ > + static __thread const char *values[sizeof(options) / > sizeof(options[0])] = { 0 }; > const char *(*ptr)[2]; > const char *value; > size_t i; > @@ -270,13 +270,10 @@ const char *lxc_global_config_value(const char > *option_name) > return NULL; > } > > - static_lock(); > if (values[i]) { > value = values[i]; > - static_unlock(); > return value; > } > - static_unlock(); > > process_lock(); > fin = fopen_cloexec(LXC_GLOBAL_CONF, "r"); > @@ -313,21 +310,17 @@ const char *lxc_global_config_value(const char > *option_name) > while (*p && (*p == ' ' || *p == '\t')) p++; > if (!*p) > continue; > - static_lock(); > values[i] = copy_global_config_value(p); > - static_unlock(); > goto out; > } > } > /* could not find value, use default */ > - static_lock(); > values[i] = (*ptr)[1]; > /* special case: if default value is NULL, > * and there is no config, don't view that > * as an error... */ > if (!values[i]) > errno = 0; > - static_unlock(); > > out: > process_lock(); > @@ -335,10 +328,7 @@ out: > fclose(fin); > process_unlock(); > > - static_lock(); > - value = values[i]; > - static_unlock(); > - return value; > + return values[i]; > } > > const char *default_lvm_vg(void) > -- > 1.8.3.2 > > _______________________________________________ > lxc-devel mailing list > [email protected] > http://lists.linuxcontainers.org/listinfo/lxc-devel _______________________________________________ lxc-devel mailing list [email protected] http://lists.linuxcontainers.org/listinfo/lxc-devel
