[PATCH] irq_work: Don't reinvent the wheel but use existing llist API

[PATCH] irq_work: Don't reinvent the wheel but use existing llist API

[Frederic Weisbecker]

From: Byungchul Park <byungchul.park@lge.com>

Although llist provides proper APIs, they are not used. Make them used.

Signed-off-by: Byungchul Park <byungchul.park@lge.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
---
 kernel/irq_work.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/kernel/irq_work.c b/kernel/irq_work.c
index bcf107c..e2ebe8c 100644
--- a/kernel/irq_work.c
+++ b/kernel/irq_work.c
@@ -138,11 +138,7 @@ static void irq_work_run_list(struct llist_head *list)
 		return;
 
 	llnode = llist_del_all(list);
-	while (llnode != NULL) {
-		work = llist_entry(llnode, struct irq_work, llnode);
-
-		llnode = llist_next(llnode);
-
+	llist_for_each_entry(work, llnode, llnode) {
 		/*
 		 * Clear the PENDING bit, after this point the @work
 		 * can be re-used.
-- 
2.7.4

[tip:irq/core] irq/work: Don't reinvent the wheel but use existing llist API

[tip-bot for Byungchul Park]

Commit-ID:  16c0890dc66d258fdeccf7b15a133f3930b19143
Gitweb:     https://git.kernel.org/tip/16c0890dc66d258fdeccf7b15a133f3930b19143
Author:     Byungchul Park <byungchul.park@lge.com>
AuthorDate: Tue, 31 Oct 2017 02:46:54 +0100
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Tue, 31 Oct 2017 10:24:39 +0100

irq/work: Don't reinvent the wheel but use existing llist API

Use the proper llist APIs instead of open-coded variants of them.

Signed-off-by: Byungchul Park <byungchul.park@lge.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1509414414-14987-1-git-send-email-frederic@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 kernel/irq_work.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/kernel/irq_work.c b/kernel/irq_work.c
index bcf107c..e2ebe8c 100644
--- a/kernel/irq_work.c
+++ b/kernel/irq_work.c
@@ -138,11 +138,7 @@ static void irq_work_run_list(struct llist_head *list)
 		return;
 
 	llnode = llist_del_all(list);
-	while (llnode != NULL) {
-		work = llist_entry(llnode, struct irq_work, llnode);
-
-		llnode = llist_next(llnode);
-
+	llist_for_each_entry(work, llnode, llnode) {
 		/*
 		 * Clear the PENDING bit, after this point the @work
 		 * can be re-used.

Re: [PATCH] irq_work: Don't reinvent the wheel but use existing llist API

[Chris Wilson]

Quoting Frederic Weisbecker (2017-10-31 01:46:54)
> From: Byungchul Park <byungchul.park@lge.com>
> 
> Although llist provides proper APIs, they are not used. Make them used.
> 
> Signed-off-by: Byungchul Park <byungchul.park@lge.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
> ---
>  kernel/irq_work.c | 6 +-----
>  1 file changed, 1 insertion(+), 5 deletions(-)
> 
> diff --git a/kernel/irq_work.c b/kernel/irq_work.c
> index bcf107c..e2ebe8c 100644
> --- a/kernel/irq_work.c
> +++ b/kernel/irq_work.c
> @@ -138,11 +138,7 @@ static void irq_work_run_list(struct llist_head *list)
>                 return;
>  
>         llnode = llist_del_all(list);
> -       while (llnode != NULL) {
> -               work = llist_entry(llnode, struct irq_work, llnode);
> -
> -               llnode = llist_next(llnode);
> -
> +       llist_for_each_entry(work, llnode, llnode) {
>                 /*
>                  * Clear the PENDING bit, after this point the @work
>                  * can be re-used.

I haven't seen this reported yet, but this requires
llist_for_each_entry_safe() because as mentioned work can be linked into
another cpu's runlist after the PENDING bit is cleared.
-Chris

[tip:irq/core] irq/work: Use llist_for_each_entry_safe

[tip-bot for Thomas Gleixner]

Commit-ID:  d00a08cf9ee986ad6689ce8c6fd176aff679c106
Gitweb:     https://git.kernel.org/tip/d00a08cf9ee986ad6689ce8c6fd176aff679c106
Author:     Thomas Gleixner <tglx@linutronix.de>
AuthorDate: Sun, 12 Nov 2017 13:02:51 +0100
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Sun, 12 Nov 2017 13:15:14 +0100

irq/work: Use llist_for_each_entry_safe

The llist_for_each_entry() loop in irq_work_run_list() is unsafe because
once the works PENDING bit is cleared it can be requeued on another CPU.

Use llist_for_each_entry_safe() instead.

Fixes: 16c0890dc66d ("irq/work: Don't reinvent the wheel but use existing llist API")
Reported-by:Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Frederic Weisbecker <frederic@kernel.org>
Cc: Byungchul Park <byungchul.park@lge.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Petri Latvala <petri.latvala@intel.com>
Link: http://lkml.kernel.org/r/151027307351.14762.4611888896020658384@mail.alporthouse.com
---
 kernel/irq_work.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/kernel/irq_work.c b/kernel/irq_work.c
index e2ebe8c..6647b33f 100644
--- a/kernel/irq_work.c
+++ b/kernel/irq_work.c
@@ -128,9 +128,9 @@ bool irq_work_needs_cpu(void)
 
 static void irq_work_run_list(struct llist_head *list)
 {
-	unsigned long flags;
-	struct irq_work *work;
+	struct irq_work *work, *tmp;
 	struct llist_node *llnode;
+	unsigned long flags;
 
 	BUG_ON(!irqs_disabled());
 
@@ -138,7 +138,7 @@ static void irq_work_run_list(struct llist_head *list)
 		return;
 
 	llnode = llist_del_all(list);
-	llist_for_each_entry(work, llnode, llnode) {
+	llist_for_each_entry_safe(work, tmp, llnode, llnode) {
 		/*
 		 * Clear the PENDING bit, after this point the @work
 		 * can be re-used.