linux/include
Jason A. Donenfeld d92cff89a0 net_dbg_ratelimited: turn into no-op when !DEBUG
The pr_debug family of functions turns into a no-op when -DDEBUG is not
specified, opting instead to call "no_printk", which gets compiled to a
no-op (but retains gcc's nice warnings about printf-style arguments).

The problem with net_dbg_ratelimited is that it is defined to be a
variant of net_ratelimited_function, which expands to essentially:

    if (net_ratelimit())
        pr_debug(fmt, ...);

When DEBUG is not defined, then this becomes,

    if (net_ratelimit())
        ;

This seems benign, except it isn't. Firstly, there's the obvious
overhead of calling net_ratelimit needlessly, which does quite some book
keeping for the rate limiting. Given that the pr_debug and
net_dbg_ratelimited family of functions are sprinkled liberally through
performance critical code, with developers assuming they'll be compiled
out to a no-op most of the time, we certainly do not want this needless
book keeping. Secondly, and most visibly, even though no debug message
is printed when DEBUG is not defined, if there is a flood of
invocations, dmesg winds up peppered with messages such as
"net_ratelimit: 320 callbacks suppressed". This is because our
aforementioned net_ratelimit() function actually prints this text in
some circumstances. It's especially odd to see this when there isn't any
other accompanying debug message.

So, in sum, it doesn't make sense to have this function's current
behavior, and instead it should match what every other debug family of
functions in the kernel does with !DEBUG -- nothing.

This patch replaces calls to net_dbg_ratelimited when !DEBUG with
no_printk, keeping with the idiom of all the other debug print helpers.

Also, though not strictly neccessary, it guards the call with an if (0)
so that all evaluation of any arguments are sure to be compiled out.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2015-08-06 23:51:30 -07:00
..
acpi Additional ACPICA material for v4.2-rc1 2015-07-02 17:11:28 -07:00
asm-generic mm: clean up per architecture MM hook header files 2015-07-17 16:39:53 -07:00
clocksource
crypto
drm drm: use kvfree() in drm_free_large() 2015-06-30 19:44:59 -07:00
dt-bindings The changes to the common clock framework for 4.2 are dominated by new 2015-07-01 19:22:00 -07:00
keys
kvm
linux net_dbg_ratelimited: turn into no-op when !DEBUG 2015-08-06 23:51:30 -07:00
math-emu
media Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/cooloney/linux-leds 2015-07-01 19:09:11 -07:00
memory
misc
net Merge git://git.kernel.org/pub/scm/linux/kernel/git/pablo/nf-next 2015-08-04 23:57:45 -07:00
pcmcia
ras tracing: add trace event for memory-failure 2015-06-24 17:49:43 -07:00
rdma IB: Add rdma_cap_ib_switch helper and use where appropriate 2015-07-14 13:20:08 -04:00
rxrpc
scsi IB/srp: Avoid using uninitialized variable 2015-07-14 13:20:09 -04:00
soc Merge branch 'for-linus' of git://ftp.arm.linux.org.uk/~rmk/linux-arm 2015-06-26 12:20:00 -07:00
sound
target iscsi-target: Fix iscsit_start_kthreads failure OOPs 2015-07-24 14:19:43 -07:00
trace Merge branch 'for-linus-4.2' of git://git.kernel.org/pub/scm/linux/kernel/git/mason/linux-btrfs 2015-06-30 20:07:45 -07:00
uapi Merge git://git.kernel.org/pub/scm/linux/kernel/git/pablo/nf-next 2015-08-04 23:57:45 -07:00
video Merge branch 'drm-next' of git://people.freedesktop.org/~airlied/linux 2015-06-26 13:18:51 -07:00
xen
Kbuild