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author | Linus Torvalds <torvalds@linux-foundation.org> | 2014-10-31 19:43:52 (GMT) |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2014-10-31 19:43:52 (GMT) |
commit | aea4869f68b5869afbb308bfb7d777d725df8900 (patch) | |
tree | 20a2c9702eb337190966f81a5cadb9bff38672d2 /kernel | |
parent | 0f4b06766bb6dc16c62c45607e3ccced23b7fead (diff) | |
parent | 21ee24bf5b43ecaeec43a7d5c61edb3cd7f847bf (diff) | |
download | linux-aea4869f68b5869afbb308bfb7d777d725df8900.tar.xz |
Merge branch 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull core fixes from Ingo Molnar:
"The tree contains two RCU fixes and a compiler quirk comment fix"
* 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
rcu: Make rcu_barrier() understand about missing rcuo kthreads
compiler/gcc4+: Remove inaccurate comment about 'asm goto' miscompiles
rcu: More on deadlock between CPU hotplug and expedited grace periods
Diffstat (limited to 'kernel')
-rw-r--r-- | kernel/cpu.c | 14 | ||||
-rw-r--r-- | kernel/rcu/tree.c | 15 | ||||
-rw-r--r-- | kernel/rcu/tree.h | 1 | ||||
-rw-r--r-- | kernel/rcu/tree_plugin.h | 33 |
4 files changed, 57 insertions, 6 deletions
diff --git a/kernel/cpu.c b/kernel/cpu.c index 356450f..90a3d01 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); diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 133e472..9815447 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -3299,11 +3299,16 @@ static void _rcu_barrier(struct rcu_state *rsp) continue; rdp = per_cpu_ptr(rsp->rda, cpu); if (rcu_is_nocb_cpu(cpu)) { - _rcu_barrier_trace(rsp, "OnlineNoCB", cpu, - rsp->n_barrier_done); - atomic_inc(&rsp->barrier_cpu_count); - __call_rcu(&rdp->barrier_head, rcu_barrier_callback, - rsp, cpu, 0); + if (!rcu_nocb_cpu_needs_barrier(rsp, cpu)) { + _rcu_barrier_trace(rsp, "OfflineNoCB", cpu, + rsp->n_barrier_done); + } else { + _rcu_barrier_trace(rsp, "OnlineNoCB", cpu, + rsp->n_barrier_done); + atomic_inc(&rsp->barrier_cpu_count); + __call_rcu(&rdp->barrier_head, + rcu_barrier_callback, rsp, cpu, 0); + } } else if (ACCESS_ONCE(rdp->qlen)) { _rcu_barrier_trace(rsp, "OnlineQ", cpu, rsp->n_barrier_done); diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h index d037646..bbdc45d 100644 --- a/kernel/rcu/tree.h +++ b/kernel/rcu/tree.h @@ -587,6 +587,7 @@ static void print_cpu_stall_info(struct rcu_state *rsp, int cpu); static void print_cpu_stall_info_end(void); static void zero_cpu_stall_ticks(struct rcu_data *rdp); static void increment_cpu_stall_ticks(void); +static bool rcu_nocb_cpu_needs_barrier(struct rcu_state *rsp, int cpu); static void rcu_nocb_gp_set(struct rcu_node *rnp, int nrq); static void rcu_nocb_gp_cleanup(struct rcu_state *rsp, struct rcu_node *rnp); static void rcu_init_one_nocb(struct rcu_node *rnp); diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index 387dd45..c1d7f27 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -2050,6 +2050,33 @@ static void wake_nocb_leader(struct rcu_data *rdp, bool force) } /* + * Does the specified CPU need an RCU callback for the specified flavor + * of rcu_barrier()? + */ +static bool rcu_nocb_cpu_needs_barrier(struct rcu_state *rsp, int cpu) +{ + struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); + struct rcu_head *rhp; + + /* No-CBs CPUs might have callbacks on any of three lists. */ + rhp = ACCESS_ONCE(rdp->nocb_head); + if (!rhp) + rhp = ACCESS_ONCE(rdp->nocb_gp_head); + if (!rhp) + rhp = ACCESS_ONCE(rdp->nocb_follower_head); + + /* Having no rcuo kthread but CBs after scheduler starts is bad! */ + if (!ACCESS_ONCE(rdp->nocb_kthread) && rhp) { + /* RCU callback enqueued before CPU first came online??? */ + pr_err("RCU: Never-onlined no-CBs CPU %d has CB %p\n", + cpu, rhp->func); + WARN_ON_ONCE(1); + } + + return !!rhp; +} + +/* * Enqueue the specified string of rcu_head structures onto the specified * CPU's no-CBs lists. The CPU is specified by rdp, the head of the * string by rhp, and the tail of the string by rhtp. The non-lazy/lazy @@ -2642,6 +2669,12 @@ static bool init_nocb_callback_list(struct rcu_data *rdp) #else /* #ifdef CONFIG_RCU_NOCB_CPU */ +static bool rcu_nocb_cpu_needs_barrier(struct rcu_state *rsp, int cpu) +{ + WARN_ON_ONCE(1); /* Should be dead code. */ + return false; +} + static void rcu_nocb_gp_cleanup(struct rcu_state *rsp, struct rcu_node *rnp) { } |