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time: jiffies_delta_to_clock_t() helper to the rescue

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Various /proc/net files sometimes report crazy timer values, expressed
in clock_t units.

This happens when an expired timer delta (expires - jiffies) is passed
to jiffies_to_clock_t().

This function has an overflow in :

return div_u64((u64)x * TICK_NSEC, NSEC_PER_SEC / USER_HZ);

commit cbbc719fcc (time: Change jiffies_to_clock_t() argument type
to unsigned long) only got around the problem.

As we cant output negative values in /proc/net/tcp without breaking
various tools, I suggest adding a jiffies_delta_to_clock_t() wrapper
that caps the negative delta to a 0 value.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Maciej Żenczykowski <maze@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: hank <pyu@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet
2012-08-08 21:13:53 +00:00
committed by David S. Miller
parent 79cda75a10
commit a399a80531
7 changed files with 22 additions and 19 deletions
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2
net/core/rtnetlink.c
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@@ -618,7 +618,7 @@ int rtnl_put_cacheinfo(struct sk_buff *skb, struct dst_entry *dst, u32 id,
long expires, u32 error)
{
struct rta_cacheinfo ci = {
.rta_lastuse = jiffies_to_clock_t(jiffies - dst->lastuse),
.rta_lastuse = jiffies_delta_to_clock_t(jiffies - dst->lastuse),
.rta_used = dst->__use,
.rta_clntref = atomic_read(&(dst->__refcnt)),
.rta_error = error,