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List:       apr-dev
Subject:    =?utf-8?B?562U5aSNOiBhcHJfcGFsbG9jIGlzIG5vdCB0aHJlYWQgc2FmZQ==?=
From:       TROY.LIU 劉春偉 <TROY.LIU () DELTAWW ! COM ! CN>
Date:       2013-05-31 14:45:14
Message-ID: 2F0AC4ECF2B4184AA4CA0686F17F298806A49AE705 () DGEX2V ! dg ! deltagroup ! com
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It was my fault to misunderstood apr pool.
My ill design was "each thread will create a condition variable with a global pool".
Temporarily I put my apr_thread_cond_create into mutex lock, and my server has been \
running well for hours. Next I prepare to let each thread create its own pool.

Thanks for your explanation.


-----邮件原件-----
发件人: Graham Leggett [mailto:minfrin@sharp.fm]
发送时间: 2013年5月31日 19:07
收件人: TROY.LIU 劉春偉
抄送: Philip Martin; dev@apr.apache.org; modules-dev@httpd.apache.org
主题: Re: apr_palloc is not thread safe

On 31 May 2013, at 6:15 AM, TROY.LIU 劉春偉 <TROY.LIU@DELTAWW.COM.CN> wrote:

> Thanks for reply, I got it.  Now the problem is my APIs does not expose apr_pool_t \
> to user like apr,  so my APIs are not thread safe.

The typical way you use a pool is that pools are arranged logically in a hierarchy. \
So a process would have a pool, then one subpool of the process pool for each thread, \
and then one subpool per unit of work (for example a connection handled by the \
thread).

It is not the job of pools to dictate to you how you should arrange your pools, that \
is your job. Trying to add mutexes to an API that doesn't need to be threadsafe is a \
waste of resources, so it is left up to you to decide how your pool usage remains \
threadsafe.

In the above example, there is no need for any locks, because the per thread pool \
would only be used by that thread. You might have a pool representing a connection, \
and you might allow that connection to be handled by any thread, but as long as just \
one thread handles that connection at any given time you get away with not needing \
locks still.

It is only when the pool is attached to something that does span threads, such as a \
database connection pool, that you start needing locks, in which case use the mutex \
APIs to use the locks you need.

Again, APR gives you choice: do you use an in-process thread lock, or a machine wide \
process lock, which you choose is up to your application's needs.

Regards,
Graham
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