提交 cb7e9704 编写于 作者: L Linus Torvalds

Merge branch 'rcu/urgent' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu

Pull RCU fixes from Paul McKenney:
 "I must confess that this past merge window was not RCU's best showing.
  This series contains three more fixes for RCU regressions:

   1.   A fix to __DECLARE_TRACE_RCU() that causes it to act as an
        interrupt from idle rather than as a task switch from idle.
        This change is needed due to the recent use of _rcuidle()
        tracepoints that can be invoked from interrupt handlers as well
        as from idle.  Without this fix, invoking _rcuidle() tracepoints
        from interrupt handlers results in splats and (more seriously)
        confusion on RCU's part as to whether a given CPU is idle or not.
        This confusion can in turn result in too-short grace periods and
        therefore random memory corruption.

   2.   A fix to a subtle deadlock that could result due to RCU doing
        a wakeup while holding one of its rcu_node structure's locks.
        Although the probability of occurrence is low, it really
        does happen.  The fix, courtesy of Steven Rostedt, uses
        irq_work_queue() to avoid the deadlock.

   3.   A fix to a silent deadlock (invisible to lockdep) due to the
        interaction of timeouts posted by RCU debug code enabled by
        CONFIG_PROVE_RCU_DELAY=y, grace-period initialization, and CPU
        hotplug operations.  This will not occur in production kernels,
        but really does occur in randconfig testing.  Diagnosis courtesy
        of Steven Rostedt"

* 'rcu/urgent' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu:
  rcu: Fix deadlock with CPU hotplug, RCU GP init, and timer migration
  rcu: Don't call wakeup() with rcu_node structure ->lock held
  trace: Allow idle-safe tracepoints to be called from irq
......@@ -145,8 +145,8 @@ static inline void tracepoint_synchronize_unregister(void)
TP_PROTO(data_proto), \
TP_ARGS(data_args), \
TP_CONDITION(cond), \
rcu_idle_exit(), \
rcu_idle_enter()); \
rcu_irq_enter(), \
rcu_irq_exit()); \
}
#else
#define __DECLARE_TRACE_RCU(name, proto, args, cond, data_proto, data_args)
......
......@@ -431,6 +431,7 @@ choice
config TREE_RCU
bool "Tree-based hierarchical RCU"
depends on !PREEMPT && SMP
select IRQ_WORK
help
This option selects the RCU implementation that is
designed for very large SMP system with hundreds or
......
......@@ -1451,9 +1451,9 @@ static int rcu_gp_init(struct rcu_state *rsp)
rnp->grphi, rnp->qsmask);
raw_spin_unlock_irq(&rnp->lock);
#ifdef CONFIG_PROVE_RCU_DELAY
if ((prandom_u32() % (rcu_num_nodes * 8)) == 0 &&
if ((prandom_u32() % (rcu_num_nodes + 1)) == 0 &&
system_state == SYSTEM_RUNNING)
schedule_timeout_uninterruptible(2);
udelay(200);
#endif /* #ifdef CONFIG_PROVE_RCU_DELAY */
cond_resched();
}
......@@ -1613,6 +1613,14 @@ static int __noreturn rcu_gp_kthread(void *arg)
}
}
static void rsp_wakeup(struct irq_work *work)
{
struct rcu_state *rsp = container_of(work, struct rcu_state, wakeup_work);
/* Wake up rcu_gp_kthread() to start the grace period. */
wake_up(&rsp->gp_wq);
}
/*
* Start a new RCU grace period if warranted, re-initializing the hierarchy
* in preparation for detecting the next grace period. The caller must hold
......@@ -1637,8 +1645,12 @@ rcu_start_gp_advanced(struct rcu_state *rsp, struct rcu_node *rnp,
}
rsp->gp_flags = RCU_GP_FLAG_INIT;
/* Wake up rcu_gp_kthread() to start the grace period. */
wake_up(&rsp->gp_wq);
/*
* We can't do wakeups while holding the rnp->lock, as that
* could cause possible deadlocks with the rq->lock. Deter
* the wakeup to interrupt context.
*/
irq_work_queue(&rsp->wakeup_work);
}
/*
......@@ -3235,6 +3247,7 @@ static void __init rcu_init_one(struct rcu_state *rsp,
rsp->rda = rda;
init_waitqueue_head(&rsp->gp_wq);
init_irq_work(&rsp->wakeup_work, rsp_wakeup);
rnp = rsp->level[rcu_num_lvls - 1];
for_each_possible_cpu(i) {
while (i > rnp->grphi)
......
......@@ -27,6 +27,7 @@
#include <linux/threads.h>
#include <linux/cpumask.h>
#include <linux/seqlock.h>
#include <linux/irq_work.h>
/*
* Define shape of hierarchy based on NR_CPUS, CONFIG_RCU_FANOUT, and
......@@ -442,6 +443,7 @@ struct rcu_state {
char *name; /* Name of structure. */
char abbr; /* Abbreviated name. */
struct list_head flavors; /* List of RCU flavors. */
struct irq_work wakeup_work; /* Postponed wakeups */
};
/* Values for rcu_state structure's gp_flags field. */
......
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