From: Mikael Pettersson <mikpe@csd.uu.se>
This patch fixes a "might sleep in illegal context" error in the
per-process performance counter inheritance changes I sent a few days ago.
The write_lock_irq() in release_task() interferes with semaphore operations
potentially done as a side-effect of freeing the task's perfctr state
object. The fix is to do the final freeing via schedule_work().
CONFIG_DEBUG_SPINLOCK_SLEEP detects the error fairly quickly.
Signed-off-by: Mikael Pettersson <mikpe@csd.uu.se>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---
25-akpm/drivers/perfctr/virtual.c | 16 +++++++++++++++-
1 files changed, 15 insertions(+), 1 deletion(-)
diff -puN drivers/perfctr/virtual.c~perfctr-inheritance-illegal-sleep-bug drivers/perfctr/virtual.c
--- 25/drivers/perfctr/virtual.c~perfctr-inheritance-illegal-sleep-bug 2004-07-26 16:51:39.059165576 -0700
+++ 25-akpm/drivers/perfctr/virtual.c 2004-07-26 16:51:39.064164816 -0700
@@ -45,6 +45,7 @@ struct vperfctr {
/* protected by task_lock(owner) */
unsigned long long inheritance_id;
struct perfctr_sum_ctrs children;
+ struct work_struct free_work;
};
#define IS_RUNNING(perfctr) perfctr_cstatus_enabled((perfctr)->cpu_state.cstatus)
@@ -160,6 +161,19 @@ static void put_vperfctr(struct vperfctr
vperfctr_free(perfctr);
}
+static void scheduled_vperfctr_free(void *perfctr)
+{
+ vperfctr_free((struct vperfctr*)perfctr);
+}
+
+static void schedule_put_vperfctr(struct vperfctr *perfctr)
+{
+ if (!atomic_dec_and_test(&perfctr->count))
+ return;
+ INIT_WORK(&perfctr->free_work, scheduled_vperfctr_free, perfctr);
+ schedule_work(&perfctr->free_work);
+}
+
static unsigned long long new_inheritance_id(void)
{
static spinlock_t lock = SPIN_LOCK_UNLOCKED;
@@ -383,7 +397,7 @@ void __vperfctr_release(struct task_stru
}
task_unlock(parent_tsk);
child_tsk->thread.perfctr = NULL;
- put_vperfctr(child_perfctr);
+ schedule_put_vperfctr(child_perfctr);
}
/* schedule() --> switch_to() --> .. --> __vperfctr_suspend().
_