linux-kernel - Re: [PATCH 1/4] irq_work: Convert flags to atomic

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Date:   Mon, 11 Nov 2019 09:00:58 +0100
From:   Ingo Molnar <mingo@...nel.org>
To:     Frederic Weisbecker <frederic@...nel.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 1/4] irq_work: Convert flags to atomic_t


* Frederic Weisbecker <frederic@...nel.org> wrote:

> We need to convert flags to atomic_t in order to later fix an ordering
> issue on cmpxchg() failure. This will allow us to use atomic_fetch_or().
> Also that clarify the nature of those flags.
> 
> Signed-off-by: Frederic Weisbecker <frederic@...nel.org>
> Cc: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Ingo Molnar <mingo@...nel.org>
> ---
>  include/linux/irq_work.h | 10 +++++++---
>  kernel/irq_work.c        | 18 +++++++++---------
>  kernel/printk/printk.c   |  2 +-
>  3 files changed, 17 insertions(+), 13 deletions(-)

You missed the irq_work use in kernel/bpf/stackmap.c - see the fix below.

Thanks,

	Ingo

===>
 kernel/bpf/stackmap.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c
index dcfe2d37ad15..23cf27ce0491 100644
--- a/kernel/bpf/stackmap.c
+++ b/kernel/bpf/stackmap.c
@@ -289,7 +289,7 @@ static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs,
 
 	if (in_nmi()) {
 		work = this_cpu_ptr(&up_read_work);
-		if (work->irq_work.flags & IRQ_WORK_BUSY)
+		if (atomic_read(&work->irq_work.flags) & IRQ_WORK_BUSY)
 			/* cannot queue more up_read, fallback */
 			irq_work_busy = true;
 	}