Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752659Ab2BTRbx (ORCPT ); Mon, 20 Feb 2012 12:31:53 -0500 Received: from mx1.redhat.com ([209.132.183.28]:17519 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751987Ab2BTRbv (ORCPT ); Mon, 20 Feb 2012 12:31:51 -0500 Date: Mon, 20 Feb 2012 18:31:47 +0100 From: Alexander Gordeev To: Thomas Gleixner Cc: Oleg Nesterov , linux-kernel@vger.kernel.org Subject: [PATCH 4/5] genirq: Get rid of unnecessary IRQTF_DIED flag Message-ID: <20120220173146.GD9313@dhcp-26-207.brq.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3567 Lines: 106 Currently IRQTF_DIED flag is set when a IRQ thread handler calls do_exit() But also PF_EXITING per process flag gets set when a thread exits. This fix eliminates the duplicate by using PF_EXITING flag. Also, there is a race condition in exit_irq_thread(). In case a thread's bit is cleared in desc->threads_oneshot (and the IRQ line gets unmasked), but before IRQTF_DIED flag is set, a new interrupt might come in and set just cleared bit again, this time forever. This fix throws IRQTF_DIED flag away, eliminating the race as a result. Reported-by: Oleg Nesterov Signed-off-by: Alexander Gordeev --- kernel/exit.c | 4 ++-- kernel/irq/handle.c | 4 ++-- kernel/irq/internals.h | 2 -- kernel/irq/manage.c | 11 +---------- 4 files changed, 5 insertions(+), 16 deletions(-) diff --git a/kernel/exit.c b/kernel/exit.c index 4b4042f..752d2c0 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -935,8 +935,6 @@ void do_exit(long code) schedule(); } - exit_irq_thread(); - exit_signals(tsk); /* sets PF_EXITING */ /* * tsk->flags are checked in the futex code to protect against @@ -945,6 +943,8 @@ void do_exit(long code) smp_mb(); raw_spin_unlock_wait(&tsk->pi_lock); + exit_irq_thread(); + if (unlikely(in_atomic())) printk(KERN_INFO "note: %s[%d] exited with preempt_count %d\n", current->comm, task_pid_nr(current), diff --git a/kernel/irq/handle.c b/kernel/irq/handle.c index 470d08c..42a32ec 100644 --- a/kernel/irq/handle.c +++ b/kernel/irq/handle.c @@ -60,8 +60,8 @@ static void irq_wake_thread(struct irq_desc *desc, struct irqaction *action) * device interrupt, so no irq storm is lurking. If the * RUNTHREAD bit is already set, nothing to do. */ - if (test_bit(IRQTF_DIED, &action->thread_flags) || - test_and_set_bit(IRQTF_RUNTHREAD, &action->thread_flags)) + if (test_and_set_bit(IRQTF_RUNTHREAD, &action->thread_flags) || + (action->thread->flags & PF_EXITING)) return; /* diff --git a/kernel/irq/internals.h b/kernel/irq/internals.h index b795231..5c233e0 100644 --- a/kernel/irq/internals.h +++ b/kernel/irq/internals.h @@ -20,14 +20,12 @@ extern bool noirqdebug; /* * Bits used by threaded handlers: * IRQTF_RUNTHREAD - signals that the interrupt handler thread should run - * IRQTF_DIED - handler thread died * IRQTF_WARNED - warning "IRQ_WAKE_THREAD w/o thread_fn" has been printed * IRQTF_AFFINITY - irq thread is requested to adjust affinity * IRQTF_FORCED_THREAD - irq action is force threaded */ enum { IRQTF_RUNTHREAD, - IRQTF_DIED, IRQTF_WARNED, IRQTF_AFFINITY, IRQTF_FORCED_THREAD, diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c index 3feab4a..a94466d 100644 --- a/kernel/irq/manage.c +++ b/kernel/irq/manage.c @@ -845,17 +845,8 @@ void exit_irq_thread(void) desc = irq_to_desc(action->irq); - /* - * Prevent a stale desc->threads_oneshot. Must be called - * before setting the IRQTF_DIED flag. - */ + /* Prevent a stale desc->threads_oneshot */ irq_finalize_oneshot(desc, action, true); - - /* - * Set the THREAD DIED flag to prevent further wakeups of the - * soon to be gone threaded handler. - */ - set_bit(IRQTF_DIED, &action->flags); } static void irq_setup_forced_threading(struct irqaction *new) -- 1.7.7.6 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/