From: Peter Zijlstra <peterz@infradead.org>
To: Jan Kara <jack@suse.cz>
Cc: Petr Mladek <pmladek@suse.com>,
Matt Fleming <matt@codeblueprint.co.uk>,
Ingo Molnar <mingo@kernel.org>,
Byungchul Park <byungchul.park@lge.com>,
Frederic Weisbecker <fweisbec@gmail.com>,
Luca Abeni <luca.abeni@unitn.it>, Rik van Riel <riel@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
Wanpeng Li <wanpeng.li@hotmail.com>,
Yuyang Du <yuyang.du@intel.com>,
Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
linux-kernel@vger.kernel.org,
Mel Gorman <mgorman@techsingularity.net>,
Mike Galbraith <umgwanakikbuti@gmail.com>
Subject: Re: [PATCH v2 7/7] sched/core: Add debug code to catch missing update_rq_clock()
Date: Thu, 22 Sep 2016 12:17:25 +0200 [thread overview]
Message-ID: <20160922101725.GK5020@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <20160922093909.GW5012@twins.programming.kicks-ass.net>
On Thu, Sep 22, 2016 at 11:39:09AM +0200, Peter Zijlstra wrote:
> bit banging the serial port is absolutely awesome, the rest of printk
> not so much.
I also have this second patch that goes on top of this.
I think I had more hacks (like using the per-cpu NMI buffers for output
instead of the on-stack thing), but I cannot seem to find them just now.
---
kernel/printk/printk.c | 16 +++++++++++++++-
1 file changed, 15 insertions(+), 1 deletion(-)
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -356,14 +356,28 @@ static int __init force_early_printk_set
}
early_param("force_early_printk", force_early_printk_setup);
+static int early_printk_cpu = -1;
+
static int early_vprintk(const char *fmt, va_list args)
{
+ int n, cpu, old;
char buf[512];
- int n;
+
+ cpu = get_cpu();
+ for (;;) {
+ old = cmpxchg(&early_printk_cpu, -1, cpu);
+ if (old == -1 || old == cpu)
+ break;
+
+ cpu_relax();
+ }
n = vscnprintf(buf, sizeof(buf), fmt, args);
early_console->write(early_console, buf, n);
+ smp_store_release(&early_printk_cpu, old);
+ put_cpu();
+
return n;
}
next prev parent reply other threads:[~2016-09-22 11:22 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-21 13:38 [PATCH v2 0/7] sched: Diagnostic checks for missing rq clock updates Matt Fleming
2016-09-21 13:38 ` [PATCH v2 1/7] sched/fair: Update the rq clock before detaching tasks Matt Fleming
2016-10-03 12:49 ` Peter Zijlstra
2016-10-03 14:37 ` Matt Fleming
2016-10-03 14:42 ` Peter Zijlstra
2016-09-21 13:38 ` [PATCH v2 2/7] sched/fair: Update rq clock before waking up new task Matt Fleming
2016-09-21 13:38 ` [PATCH v2 3/7] sched/fair: Update rq clock in task_hot() Matt Fleming
2016-09-21 13:38 ` [PATCH v2 4/7] sched: Add wrappers for lockdep_(un)pin_lock() Matt Fleming
2017-01-14 12:40 ` [tip:sched/core] sched/core: " tip-bot for Matt Fleming
2016-09-21 13:38 ` [PATCH v2 5/7] sched/core: Reset RQCF_ACT_SKIP before unpinning rq->lock Matt Fleming
2017-01-14 12:41 ` [tip:sched/core] " tip-bot for Matt Fleming
2016-09-21 13:38 ` [PATCH v2 6/7] sched/fair: Push rq lock pin/unpin into idle_balance() Matt Fleming
2017-01-14 12:41 ` [tip:sched/core] " tip-bot for Matt Fleming
2016-09-21 13:38 ` [PATCH v2 7/7] sched/core: Add debug code to catch missing update_rq_clock() Matt Fleming
2016-09-21 15:58 ` Petr Mladek
2016-09-21 19:08 ` Matt Fleming
2016-09-21 19:46 ` Thomas Gleixner
2016-09-22 0:44 ` Sergey Senozhatsky
2016-09-22 8:04 ` Peter Zijlstra
2016-09-22 8:36 ` Jan Kara
2016-09-22 9:39 ` Peter Zijlstra
2016-09-22 10:17 ` Peter Zijlstra [this message]
2017-01-14 12:44 ` [tip:sched/core] sched/core: Add debugging code to catch missing update_rq_clock() calls tip-bot for Matt Fleming
[not found] ` <87tw8gutp6.fsf@concordia.ellerman.id.au>
2017-01-30 21:34 ` Matt Fleming
2017-01-31 8:35 ` Michael Ellerman
2017-01-31 11:00 ` Sachin Sant
2017-01-31 11:48 ` Mike Galbraith
2017-01-31 17:22 ` Ross Zwisler
2017-02-02 15:55 ` Peter Zijlstra
2017-02-02 22:01 ` Matt Fleming
2017-02-03 3:05 ` Mike Galbraith
2017-02-03 4:33 ` Sachin Sant
2017-02-03 8:53 ` Peter Zijlstra
2017-02-03 12:59 ` Mike Galbraith
2017-02-03 13:37 ` Peter Zijlstra
2017-02-03 13:52 ` Mike Galbraith
2017-02-03 15:44 ` Paul E. McKenney
2017-02-03 15:54 ` Paul E. McKenney
2017-02-06 6:23 ` Sachin Sant
2017-02-06 15:10 ` Paul E. McKenney
2017-02-06 15:14 ` Paul E. McKenney
2017-02-03 13:04 ` Borislav Petkov
2017-02-22 9:03 ` Wanpeng Li
2017-02-24 9:16 ` [tip:sched/urgent] sched/core: Fix update_rq_clock() splat on hotplug (and suspend/resume) tip-bot for Peter Zijlstra
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