From: Greg Kurz <groug@kaod.org>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Daniel P. Berrangé" <berrange@redhat.com>,
qemu-devel@nongnu.org, "Alex Bennée" <alex.bennee@linaro.org>,
"Richard Henderson" <richard.henderson@linaro.org>
Subject: Re: [PATCH v2 1/2] util/log: Derive thread id from getpid() on hosts w/o gettid() syscall
Date: Fri, 21 Oct 2022 16:08:48 +0200 [thread overview]
Message-ID: <20221021160848.28ff96a4@bahia> (raw)
In-Reply-To: <e5d785bb-3865-75a3-f1aa-c99acf127c5f@redhat.com>
On Thu, 20 Oct 2022 12:39:41 +0200
Paolo Bonzini <pbonzini@redhat.com> wrote:
> On 10/19/22 17:57, Daniel P. Berrangé wrote:
> >> + if (my_id == -1) {
> >> + my_id = getpid() + qatomic_fetch_inc(&counter);
> >> + }
> >> + return my_id;
> > This doesn't look safe for linux-user when we fork, but don't exec.
>
> Linux-user won't ever get here, however bsd-user might. We should have
> get_thread_id() somewhere in util/, for example
>
> https://github.com/wine-mirror/wine/blob/master/dlls/ntdll/unix/server.c
>
We have qemu_get_thread_id() already :
https://git.qemu.org/?p=qemu.git;a=blob;f=util/oslib-posix.c;h=827a7aadba444cdb128284f5b4ba43934c78c3db;hb=HEAD#l96
> > The getpid() will change after the fork, but counter won't be
> > reset, so a thread in the parent could clash with a thread
> > in the forked child.
>
> It might clash even if the counter is reset for that matter.
>
Yes.
> Paolo
>
next prev parent reply other threads:[~2022-10-21 14:09 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-19 15:16 [PATCH v2 0/2] util/log: Always send errors to logfile when daemonized Greg Kurz
2022-10-19 15:16 ` [PATCH v2 1/2] util/log: Derive thread id from getpid() on hosts w/o gettid() syscall Greg Kurz
2022-10-19 15:57 ` Daniel P. Berrangé
2022-10-20 8:40 ` Greg Kurz
2022-10-20 10:39 ` Paolo Bonzini
2022-10-21 14:08 ` Greg Kurz [this message]
2022-10-19 15:16 ` [PATCH v2 2/2] util/log: Always send errors to logfile when daemonized Greg Kurz
2022-10-20 2:21 ` Richard Henderson
2022-10-20 9:49 ` Greg Kurz
2022-10-20 9:58 ` Daniel P. Berrangé
2022-10-20 10:52 ` Paolo Bonzini
2022-10-24 9:44 ` Alex Bennée
2022-10-25 8:52 ` Greg Kurz
2022-10-25 9:20 ` Paolo Bonzini
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