From: Steven Rostedt <rostedt@goodmis.org>
To: Joerg Roedel <jroedel@suse.de>
Cc: LKML <linux-kernel@vger.kernel.org>,
Ingo Molnar <mingo@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Peter Zijlstra <peterz@infradead.org>,
Borislav Petkov <bp@alien8.de>,
Andrew Morton <akpm@linux-foundation.org>,
Shile Zhang <shile.zhang@linux.alibaba.com>,
Andy Lutomirski <luto@amacapital.net>,
"Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
Tzvetomir Stoyanov <tz.stoyanov@gmail.com>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Subject: Re: [RFC][PATCH] x86/mm: Sync all vmalloc mappings before text_poke()
Date: Wed, 29 Apr 2020 12:52:45 -0400 [thread overview]
Message-ID: <20200429125245.5a804f62@gandalf.local.home> (raw)
In-Reply-To: <20200429162026.GT30814@suse.de>
On Wed, 29 Apr 2020 18:20:26 +0200
Joerg Roedel <jroedel@suse.de> wrote:
> On Wed, Apr 29, 2020 at 06:17:47PM +0200, Joerg Roedel wrote:
> > On Wed, Apr 29, 2020 at 10:07:31AM -0400, Steven Rostedt wrote:
> > > Talking with Mathieu about this on IRC, he pointed out that my code does
> > > have a vzalloc() that is called:
> > >
> > > in trace_pid_write()
> > >
> > > pid_list->pids = vzalloc((pid_list->pid_max + 7) >> 3);
> > >
> > > This is done when -P1,2 is on the trace-cmd command line.
> >
> > And that buffer is written to at any function entry?
>
> What I meant to say, is it possible that the page-fault handler does not
> complete because at its beginning it calls into trace-code and faults
> again on the same address?
>
It should be read only at sched_switch.
Basically, it's a big bitmask, where each bit represents a possible process
id (can be 2 gigs if we allow all positive ints!).
Then, it is only written when setting it up. Bits 1 and 2 are set here
(-P1,2). At context switch, next->pid is checked against this bitmask, and
if it is set, it means we should allow this process to be traced.
This mask should only be accessed at sched_switch time, not at other times.
And it may read any possible page in that mask depending on the process id
of the next task to be scheduled in.
-- Steve
next prev parent reply other threads:[~2020-04-29 16:52 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-29 9:48 [RFC][PATCH] x86/mm: Sync all vmalloc mappings before text_poke() Steven Rostedt
2020-04-29 10:59 ` Joerg Roedel
2020-04-29 12:28 ` Steven Rostedt
2020-04-29 14:07 ` Steven Rostedt
2020-04-29 14:10 ` Joerg Roedel
2020-04-29 14:32 ` Steven Rostedt
2020-04-29 15:44 ` Peter Zijlstra
2020-04-29 16:17 ` Joerg Roedel
2020-04-29 16:20 ` Joerg Roedel
2020-04-29 16:52 ` Steven Rostedt [this message]
2020-04-29 17:29 ` Mathieu Desnoyers
2020-04-29 18:51 ` Peter Zijlstra
2020-04-30 14:11 ` Joerg Roedel
2020-04-30 14:50 ` Joerg Roedel
2020-04-30 15:20 ` Mathieu Desnoyers
2020-04-30 16:16 ` Steven Rostedt
2020-04-30 16:18 ` Mathieu Desnoyers
2020-04-30 16:30 ` Steven Rostedt
2020-04-30 16:35 ` Mathieu Desnoyers
2020-04-30 15:23 ` Mathieu Desnoyers
2020-04-30 16:12 ` Steven Rostedt
2020-04-30 16:11 ` Steven Rostedt
2020-04-30 16:16 ` Mathieu Desnoyers
2020-04-30 16:25 ` Steven Rostedt
2020-04-30 19:14 ` Joerg Roedel
2020-05-01 1:13 ` Steven Rostedt
2020-05-01 2:26 ` Mathieu Desnoyers
2020-05-01 2:39 ` Steven Rostedt
2020-05-01 10:16 ` Joerg Roedel
2020-05-01 13:35 ` Mathieu Desnoyers
2020-05-04 15:12 ` [PATCH] percpu: Sync vmalloc mappings in pcpu_alloc() and free_percpu() Joerg Roedel
2020-05-04 15:28 ` Mathieu Desnoyers
2020-05-04 15:31 ` Joerg Roedel
2020-05-04 15:38 ` Mathieu Desnoyers
2020-05-04 15:51 ` Joerg Roedel
2020-05-04 17:04 ` Steven Rostedt
2020-05-04 17:40 ` Steven Rostedt
2020-05-04 18:38 ` Joerg Roedel
2020-05-04 19:10 ` Steven Rostedt
2020-05-05 12:31 ` [PATCH] tracing: Call vmalloc_sync_mappings() after alloc_percpu() Joerg Roedel
2020-05-06 15:17 ` Steven Rostedt
2020-05-08 14:42 ` Joerg Roedel
2020-05-04 20:25 ` [PATCH] percpu: Sync vmalloc mappings in pcpu_alloc() and free_percpu() Peter Zijlstra
2020-05-04 20:43 ` Steven Rostedt
2020-05-01 4:20 ` [RFC][PATCH] x86/mm: Sync all vmalloc mappings before text_poke() Steven Rostedt
2020-05-01 13:22 ` Mathieu Desnoyers
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