diff options
Diffstat (limited to 'rcu-More-on-deadlock-between-CPU-hotplug-and-expedit.patch')
| -rw-r--r-- | rcu-More-on-deadlock-between-CPU-hotplug-and-expedit.patch | 67 |
1 files changed, 0 insertions, 67 deletions
diff --git a/rcu-More-on-deadlock-between-CPU-hotplug-and-expedit.patch b/rcu-More-on-deadlock-between-CPU-hotplug-and-expedit.patch deleted file mode 100644 index 77770ff12..000000000 --- a/rcu-More-on-deadlock-between-CPU-hotplug-and-expedit.patch +++ /dev/null @@ -1,67 +0,0 @@ -From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> -Date: Wed, 22 Oct 2014 10:00:05 -0700 -Subject: [PATCH] rcu: More on deadlock between CPU hotplug and expedited grace - periods - -Commit dd56af42bd82 (rcu: Eliminate deadlock between CPU hotplug and -expedited grace periods) was incomplete. Although it did eliminate -deadlocks involving synchronize_sched_expedited()'s acquisition of -cpu_hotplug.lock via get_online_cpus(), it did nothing about the similar -deadlock involving acquisition of this same lock via put_online_cpus(). -This deadlock became apparent with testing involving hibernation. - -This commit therefore changes put_online_cpus() acquisition of this lock -to be conditional, and increments a new cpu_hotplug.puts_pending field -in case of acquisition failure. Then cpu_hotplug_begin() checks for this -new field being non-zero, and applies any changes to cpu_hotplug.refcount. - -Reported-by: Jiri Kosina <jkosina@suse.cz> -Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> -Tested-by: Jiri Kosina <jkosina@suse.cz> -Tested-by: Borislav Petkov <bp@suse.de> ---- - kernel/cpu.c | 14 +++++++++++++- - 1 file changed, 13 insertions(+), 1 deletion(-) - -diff --git a/kernel/cpu.c b/kernel/cpu.c -index 356450f09c1f..90a3d017b90c 100644 ---- a/kernel/cpu.c -+++ b/kernel/cpu.c -@@ -64,6 +64,8 @@ static struct { - * an ongoing cpu hotplug operation. - */ - int refcount; -+ /* And allows lockless put_online_cpus(). */ -+ atomic_t puts_pending; - - #ifdef CONFIG_DEBUG_LOCK_ALLOC - struct lockdep_map dep_map; -@@ -113,7 +115,11 @@ void put_online_cpus(void) - { - if (cpu_hotplug.active_writer == current) - return; -- mutex_lock(&cpu_hotplug.lock); -+ if (!mutex_trylock(&cpu_hotplug.lock)) { -+ atomic_inc(&cpu_hotplug.puts_pending); -+ cpuhp_lock_release(); -+ return; -+ } - - if (WARN_ON(!cpu_hotplug.refcount)) - cpu_hotplug.refcount++; /* try to fix things up */ -@@ -155,6 +161,12 @@ void cpu_hotplug_begin(void) - cpuhp_lock_acquire(); - for (;;) { - mutex_lock(&cpu_hotplug.lock); -+ if (atomic_read(&cpu_hotplug.puts_pending)) { -+ int delta; -+ -+ delta = atomic_xchg(&cpu_hotplug.puts_pending, 0); -+ cpu_hotplug.refcount -= delta; -+ } - if (likely(!cpu_hotplug.refcount)) - break; - __set_current_state(TASK_UNINTERRUPTIBLE); --- -1.9.3 - |