[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH v2 4/4] xen/rcu: add assertions to debug build
On 24.02.20 12:31, Roger Pau Monné wrote: On Tue, Feb 18, 2020 at 01:21:14PM +0100, Juergen Gross wrote:Xen's RCU implementation relies on no softirq handling taking place while being in a RCU critical section. Add ASSERT()s in debug builds in order to catch any violations. For that purpose modify rcu_read_[un]lock() to use a dedicated percpu counter instead of preempt_[en|dis]able() as this enables to test that condition in __do_softirq() (ASSERT_NOT_IN_ATOMIC() is not usable there due to __cpu_up() calling process_pending_softirqs() while holding the cpu hotplug lock). Dropping the now no longer needed #include of preempt.h in rcupdate.h requires adding it in some sources. Signed-off-by: Juergen Gross <jgross@xxxxxxxx> --- xen/common/multicall.c | 1 + xen/common/rcupdate.c | 4 ++++ xen/common/softirq.c | 2 ++ xen/common/wait.c | 1 + xen/include/xen/rcupdate.h | 21 +++++++++++++++++---- 5 files changed, 25 insertions(+), 4 deletions(-) diff --git a/xen/common/multicall.c b/xen/common/multicall.c index 5a199ebf8f..67f1a23485 100644 --- a/xen/common/multicall.c +++ b/xen/common/multicall.c @@ -10,6 +10,7 @@ #include <xen/multicall.h> #include <xen/guest_access.h> #include <xen/perfc.h> +#include <xen/preempt.h> #include <xen/trace.h> #include <asm/current.h> #include <asm/hardirq.h> diff --git a/xen/common/rcupdate.c b/xen/common/rcupdate.c index e6add0b120..b03f4b44d9 100644 --- a/xen/common/rcupdate.c +++ b/xen/common/rcupdate.c @@ -46,6 +46,10 @@ #include <xen/cpu.h> #include <xen/stop_machine.h>+#ifndef NDEBUG+DEFINE_PER_CPU(unsigned int, rcu_lock_cnt); +#endif + /* Global control variables for rcupdate callback mechanism. */ static struct rcu_ctrlblk { long cur; /* Current batch number. */ diff --git a/xen/common/softirq.c b/xen/common/softirq.c index 3fe75ca3e8..18be8db0c6 100644 --- a/xen/common/softirq.c +++ b/xen/common/softirq.c @@ -30,6 +30,8 @@ static void __do_softirq(unsigned long ignore_mask, bool rcu_allowed) unsigned int i, cpu; unsigned long pending;+ ASSERT(!rcu_allowed || rcu_quiesce_allowed());+ for ( ; ; ) { /* diff --git a/xen/common/wait.c b/xen/common/wait.c index 24716e7676..9cdb174036 100644 --- a/xen/common/wait.c +++ b/xen/common/wait.c @@ -19,6 +19,7 @@ * along with this program; If not, see <http://www.gnu.org/licenses/>. */+#include <xen/preempt.h>#include <xen/sched.h> #include <xen/softirq.h> #include <xen/wait.h> diff --git a/xen/include/xen/rcupdate.h b/xen/include/xen/rcupdate.h index 87f35b7704..a5ee7fec2b 100644 --- a/xen/include/xen/rcupdate.h +++ b/xen/include/xen/rcupdate.h @@ -34,10 +34,23 @@ #include <xen/cache.h> #include <xen/spinlock.h> #include <xen/cpumask.h> -#include <xen/preempt.h> +#include <xen/percpu.h>#define __rcu +#ifndef NDEBUG+DECLARE_PER_CPU(unsigned int, rcu_lock_cnt); + +#define rcu_quiesce_disable() (this_cpu(rcu_lock_cnt))++ +#define rcu_quiesce_enable() (this_cpu(rcu_lock_cnt))--I think you need a barrier here like it's currently used in preempt_{enabled/disable}, or use arch_lock_{acquire/release}_barrier which would be better IMO. Thanks, will do that. +#define rcu_quiesce_allowed() (!this_cpu(rcu_lock_cnt))ASSERT_NOT_IN_ATOMIC should be expanded to also assert !this_cpu(rcu_lock_cnt), or else missing pairs of rcu_read_{lock/unlock} would be undetected. Good idea. Juergen _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxxx https://lists.xenproject.org/mailman/listinfo/xen-devel
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