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Date: Wed, 24 Feb 2010 11:30:20 +0800
From: Li Zefan <lizf@cn.fujitsu.com>
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Subject: Re: [PATCH v2 -mmotm 3/4] cgroups: Add simple listener of cgroup
 events to documentation
References: <1f8bd63acb6485c88f8539e009459a28fb6ad55b.1266853233.git.kirill@shutemov.name> <690745ebd257c74a1c47d552fec7fbb0b5efb7d0.1266853233.git.kirill@shutemov.name> <458c3169608cb333f390b2cb732565fec9fec67e.1266853234.git.kirill@shutemov.name>
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To: "Kirill A. Shutemov" <kirill@shutemov.name>
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> +	ret = dprintf(event_control, "%d %d %s", efd, cfd, argv[2]);

I found it won't return negative value for invalid input, though
errno is set properly.

try:
# ./cgroup_event_listner /cgroup/cgroup.procs abc

while strace shows write() does return -1:

# strace ./cgroup_event_listner /cgroup/cgroup.procs abc
...
write(6, "7 5 abc"..., 7)               = -1 EINVAL (Invalid argument)

> +	if (ret == -1) {
> +		perror("Cannot write to cgroup.event_control");
> +		goto out;
> +	}

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