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From: Thomas Monjalon <thomas@monjalon.net>
To: Stephen Hemminger <stephen@networkplumber.org>
Cc: dev@dpdk.org, honnappa.nagarahalli@arm.com, joyce.kong@arm.com,
	konstantin.ananyev@intel.com
Subject: Re: [dpdk-dev] [PATCH v2] eal/rwlock: add note about writer starvation
Date: Thu, 11 Feb 2021 23:51:37 +0100
Message-ID: <6427760.fPJ3V7j96H@thomas> (raw)
In-Reply-To: <20210114165556.31353-1-stephen@networkplumber.org>

14/01/2021 17:55, Stephen Hemminger:
> The implementation of reader/writer locks in DPDK (from first release)
> is simple and fast. But it can lead to writer starvation issues.
> 
> It is not easy to fix this without changing ABI and potentially
> breaking customer applications that are expect the unfair behavior.

typo: "are expect"

> The wikipedia page on reader-writer problem has a similar example
> which summarizes the problem pretty well.

Maybe add the URL in the commit message?

> 
> Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
> ---
> --- a/lib/librte_eal/include/generic/rte_rwlock.h
> +++ b/lib/librte_eal/include/generic/rte_rwlock.h
> + * Note: This version of reader/writer locks is not fair because
> + * readers do not block for pending writers. A stream of readers can
> + * subsequently lock out all potential writers and starve them.
> + * This is because after the first reader locks the resource,
> + * no writer can lock it. The writer will only be able to get the lock
> + * when it will only be released by the last reader.

You did not get review, probably because nobody was Cc'ed.
+Cc Honnappa, Joyce and Konstantin



  reply	other threads:[~2021-02-11 22:51 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-08 19:13 [dpdk-dev] Reader-Writer lock starvation issues Stephen Hemminger
2021-01-08 21:27 ` Honnappa Nagarahalli
2021-01-11 11:52   ` Ferruh Yigit
2021-01-11 13:05     ` Honnappa Nagarahalli
2021-01-12  1:04 ` [dpdk-dev] [PATCH] eal/rwlock: add note about writer starvation Stephen Hemminger
2021-01-14 16:55   ` [dpdk-dev] [PATCH v2] " Stephen Hemminger
2021-02-11 22:51     ` Thomas Monjalon [this message]
2021-02-12  0:21       ` Honnappa Nagarahalli
2021-05-12 19:10         ` Thomas Monjalon

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