linux-kernel - [PATCH 1/6] Free up pf flag PF

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Date:	Wed, 20 Oct 2010 15:48:57 -0700
From:	Venkatesh Pallipadi <venki@...gle.com>
To:	Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...e.hu>,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	Martin Schwidefsky <schwidefsky@...ibm.com>
Cc:	linux-kernel@...r.kernel.org, Paul Turner <pjt@...gle.com>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Shaun Ruffell <sruffell@...ium.com>,
	Yong Zhang <yong.zhang0@...il.com>,
	Venkatesh Pallipadi <venki@...gle.com>
Subject: [PATCH 1/6] Free up pf flag PF_KSOFTIRQD

Cleanup patch, freeing up PF_KSOFTIRQD and
using (current == __get_cpu_var(ksoftirqd)) instead, as suggested
by Eric Dumazet.

Unrelated one line cleanup of changing hardirq_count() to in_irq() in
account_system_vtime.

Signed-off-by: Venkatesh Pallipadi <venki@...gle.com>
Cc: Eric Dumazet <eric.dumazet@...il.com>
---
 include/linux/sched.h |    3 ++-
 kernel/sched.c        |    4 ++--
 kernel/softirq.c      |    6 +++++-
 3 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 0383601..6dd4894 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1691,7 +1691,6 @@ extern void thread_group_times(struct task_struct *p, cputime_t *ut, cputime_t *
 /*
  * Per process flags
  */
-#define PF_KSOFTIRQD	0x00000001	/* I am ksoftirqd */
 #define PF_STARTING	0x00000002	/* being created */
 #define PF_EXITING	0x00000004	/* getting shut down */
 #define PF_EXITPIDONE	0x00000008	/* pi exit done on shut down */
@@ -1749,6 +1748,8 @@ extern void thread_group_times(struct task_struct *p, cputime_t *ut, cputime_t *
 #define tsk_used_math(p) ((p)->flags & PF_USED_MATH)
 #define used_math() tsk_used_math(current)
 
+int is_ksoftirqd_context(void);
+
 #ifdef CONFIG_PREEMPT_RCU
 
 #define RCU_READ_UNLOCK_BLOCKED (1 << 0) /* blocked while in RCU read-side. */
diff --git a/kernel/sched.c b/kernel/sched.c
index abf8440..5d4afe9 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -1984,9 +1984,9 @@ void account_system_vtime(struct task_struct *curr)
 	 * in that case, so as not to confuse scheduler with a special task
 	 * that do not consume any time, but still wants to run.
 	 */
-	if (hardirq_count())
+	if (in_irq())
 		per_cpu(cpu_hardirq_time, cpu) += delta;
-	else if (in_serving_softirq() && !(curr->flags & PF_KSOFTIRQD))
+	else if (in_serving_softirq() && !(is_ksoftirqd_context()))
 		per_cpu(cpu_softirq_time, cpu) += delta;
 
 	local_irq_restore(flags);
diff --git a/kernel/softirq.c b/kernel/softirq.c
index f02a9df..3ceb560 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -56,6 +56,11 @@ static struct softirq_action softirq_vec[NR_SOFTIRQS] __cacheline_aligned_in_smp
 
 static DEFINE_PER_CPU(struct task_struct *, ksoftirqd);
 
+int is_ksoftirqd_context(void)
+{
+	return (current == __get_cpu_var(ksoftirqd));
+}
+
 char *softirq_to_name[NR_SOFTIRQS] = {
 	"HI", "TIMER", "NET_TX", "NET_RX", "BLOCK", "BLOCK_IOPOLL",
 	"TASKLET", "SCHED", "HRTIMER",	"RCU"
@@ -719,7 +724,6 @@ static int run_ksoftirqd(void * __bind_cpu)
 {
 	set_current_state(TASK_INTERRUPTIBLE);
 
-	current->flags |= PF_KSOFTIRQD;
 	while (!kthread_should_stop()) {
 		preempt_disable();
 		if (!local_softirq_pending()) {
-- 
1.7.1

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