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Date: Mon, 22 Aug 2016 09:17:37 +0200
From: Jiri Olsa <jolsa@redhat.com>
To: Vegard Nossum <vegard.nossum@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
        Stephane Eranian <eranian@google.com>,
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        linux-tip-commits@vger.kernel.org
Subject: Re: [tip:perf/core] perf/core: Check return value of the
 perf_event_read() IPI
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On Sun, Aug 21, 2016 at 02:10:07PM +0200, Vegard Nossum wrote:

SNIP

> [<ffffffff816d1577>] ? __fget+0x47/0x270
> [<ffffffff81676d5b>] vfs_readv+0x8b/0xc0
> [<ffffffff81676e6e>] do_readv+0xde/0x230
> [<ffffffff81676d90>] ? vfs_readv+0xc0/0xc0
> [<ffffffff81002b60>] ? exit_to_usermode_loop+0x190/0x190
> [<ffffffff82001b07>] ? check_preemption_disabled+0x37/0x1e0
> [<ffffffff81677617>] SyS_readv+0x27/0x30
> [<ffffffff816775f0>] ? do_pwritev+0x1a0/0x1a0
> [<ffffffff81005524>] do_syscall_64+0x1c4/0x4e0
> [<ffffffff83c3286a>] entry_SYSCALL64_slow_path+0x25/0x25
> 
> I don't think WARN() is the right interface for signalling errors to
> userspace programs?

any special way to trigger that?

thanks,
jirka