From: Szabolcs Nagy <szabolcs.nagy@arm.com>
To: Yubin Ruan <ablacktshirt@gmail.com>, libc-help@sourceware.org
Cc: nd@arm.com
Subject: Re: determine whether code is running in a signal handler context
Date: Fri, 20 Oct 2017 10:32:00 -0000 [thread overview]
Message-ID: <59E9D0C2.4090900@arm.com> (raw)
In-Reply-To: <CAJYFCiPkMNCr0X61AQ9MqhXyagOb0k4tTp5mRAD171VLkedVYQ@mail.gmail.com>
On 18/10/17 15:18, Yubin Ruan wrote:
> Hi,
>
> I am writing to see if this is any util functions in libc that can
> help to determine it is currently running in a signal.
>
> I wrote some library and provide a function which will be used in many
> client code. However this function is not async-signal safe (it calls
> malloc(3)) so when it is called, I want to detect whether it is
> currently running in a signal handler. If it is, I can avoid calling
> those not-async-signal-safe functions which might cause deadlock.
>
note that in posix as-safety is symmetric between the
interrupted code and interrupt handler: if any of the
interrupt and interrupt handler is as-safe then the
behaviour is well defined.
so calling non-as-safe code in an asynchronous signal
handler is perfectly fine if the interrupted code is
as-safe.
there are synchronous signals too, i.e. raise(sig),
and then the signal handler runs in well-defined state
(one can use signal masks to make sure a signal handler
only runs in such state)
so using "in_signal_handler_context()" is not a valid
way to verify the as-safety interface contract.
> that is, I want a `in_signal_handler_context()' utility that can be
> used as this:
>
> int mylibfunc( void ) {
> if( in_signal_handler_context() ) { return(-1) }
> // rest of function goes here
> return( 0 );
> }
>
>
> Yubin
>
next prev parent reply other threads:[~2017-10-20 10:32 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-18 14:18 Yubin Ruan
2017-10-18 18:34 ` Carlos O'Donell
2017-10-19 1:52 ` Yubin Ruan
2017-10-19 2:19 ` Carlos O'Donell
2017-10-19 2:39 ` Will Hawkins
2017-10-19 3:12 ` Carlos O'Donell
2017-10-19 4:07 ` Yubin Ruan
2017-10-19 4:56 ` Carlos O'Donell
2017-10-19 4:19 ` Will Hawkins
2017-10-19 4:01 ` Yubin Ruan
2017-10-19 2:59 ` Sean Conner
2017-10-19 3:12 ` Sean Conner
2017-10-19 3:51 ` Yubin Ruan
2017-10-19 7:10 ` Jeffrey Walton
2017-10-20 10:32 ` Szabolcs Nagy [this message]
2017-10-20 11:23 ` Yubin Ruan
2017-10-20 11:31 ` Szabolcs Nagy
2017-10-20 17:19 ` Carlos O'Donell
2017-10-20 17:48 ` Szabolcs Nagy
2017-10-22 6:09 ` Carlos O'Donell
2017-10-22 23:39 ` where is the definition of idtype_t supposed to live? John Lumby
2017-10-23 13:57 ` Florian Weimer
[not found] ` <BN6PR22MB16662DE3DFB590B3D6006F81A3460@BN6PR22MB1666.namprd22.prod.outlook.com>
2017-10-23 14:20 ` Florian Weimer
2017-10-23 10:01 ` determine whether code is running in a signal handler context Szabolcs Nagy
2017-10-23 14:30 ` Carlos O'Donell
2017-10-24 1:00 ` Yubin Ruan
2017-11-27 8:43 ` Yubin Ruan
2017-11-27 11:55 ` Florian Weimer
2017-11-27 12:50 ` Yubin Ruan
2017-11-27 12:51 ` Florian Weimer
2017-11-27 12:58 ` Adhemerval Zanella
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