[patch] pthread_cond_wait and pthread_cond_timedwait can also return EPERM

[patch] pthread_cond_wait and pthread_cond_timedwait can also return EPERM

[Jan Kratochvil]

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pthread_cond_wait and pthread_cond_timedwait can also return EPERM

Attached a reproducer.

I did not test the EINTR case but it looks logical to me.

Signed-off-by: Jan Kratochvil <jan@jankratochvil.net>

[-- Attachment #2: wait.c --]
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#define _GNU_SOURCE
#include <pthread.h>
#include <assert.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
int main(void) {
//  pthread_mutex_t mut = PTHREAD_MUTEX_INITIALIZER; // not reproducible
  pthread_mutex_t mut = PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP;
  pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
  int err;
//  err=pthread_mutex_lock(&mut);
//  assert(!err);
  err=pthread_cond_wait(&cond, &mut);
  if (err) {
    printf("%d=%s\n",err,strerror(err));
    return 1;
  }
  return 0;
}

[-- Attachment #3: pthread_cond_init.3.patch --]
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diff --git a/man/man3/pthread_cond_init.3 b/man/man3/pthread_cond_init.3
index 42e7eac..6e21b54 100644
--- a/man/man3/pthread_cond_init.3
+++ b/man/man3/pthread_cond_init.3
@@ -141,15 +141,28 @@ and a non-zero error code on error.
 .
 .SH ERRORS
 \fBpthread_cond_init\fP,
-\fBpthread_cond_signal\fP,
-\fBpthread_cond_broadcast\fP,
-and \fBpthread_cond_wait\fP
+\fBpthread_cond_signal\fP
+and \fBpthread_cond_broadcast\fP,
 never return an error code.
 .P
+The \fBpthread_cond_wait\fP function returns
+the following error codes on error:
+.RS
+.TP
+\fBEPERM\fP
+\fBmutex\fP is not locked.
+.TP
+\fBEINTR\fP
+\fBpthread_cond_wait\fP was interrupted by a signal.
+.RE
+.P
 The \fBpthread_cond_timedwait\fP function returns
 the following error codes on error:
 .RS
 .TP
+\fBEPERM\fP
+\fBmutex\fP is not locked.
+.TP
 \fBETIMEDOUT\fP
 The condition variable was not signaled
 until the timeout specified by \fIabstime\fP.

Re: [patch] pthread_cond_wait and pthread_cond_timedwait can also return EPERM

[Florian Weimer]

* Jan Kratochvil:

> +\fBEINTR\fP
> +\fBpthread_cond_wait\fP was interrupted by a signal.
> +.RE

POSIX specifically disallows returning EINTR.  Applications cannot
expect that pthread_cond_wait returns upon delivery of a signal.  Such
a return is only possible due to the general allowance for spurious
wakeups, and must result in a zero result.

Re: [patch] pthread_cond_wait and pthread_cond_timedwait can also return EPERMignalignal

[Jan Kratochvil]

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On Thu, 10 Oct 2024 18:32:51 +0800, Florian Weimer wrote:
> * Jan Kratochvil:
> 
> > +\fBEINTR\fP
> > +\fBpthread_cond_wait\fP was interrupted by a signal.
> > +.RE
> 
> POSIX specifically disallows returning EINTR.  Applications cannot
> expect that pthread_cond_wait returns upon delivery of a signal.  Such
> a return is only possible due to the general allowance for spurious
> wakeups, and must result in a zero result.

OK, I agree when I tried that. So I have removed this part.

But then I believe the EINTR presence at pthread_cond_timedwait documentation
is also wrong (I did not change that in this patch) as I could not reproduce
the EINTR (attached).


Jan


Signed-off-by: Jan Kratochvil <jan@jankratochvil.net>

[-- Attachment #2: pthread_cond_init.3.patch --]
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diff --git a/man/man3/pthread_cond_init.3 b/man/man3/pthread_cond_init.3
index 42e7eac..fa4c6f6 100644
--- a/man/man3/pthread_cond_init.3
+++ b/man/man3/pthread_cond_init.3
@@ -141,15 +141,25 @@ and a non-zero error code on error.
 .
 .SH ERRORS
 \fBpthread_cond_init\fP,
-\fBpthread_cond_signal\fP,
-\fBpthread_cond_broadcast\fP,
-and \fBpthread_cond_wait\fP
+\fBpthread_cond_signal\fP
+and \fBpthread_cond_broadcast\fP,
 never return an error code.
 .P
+The \fBpthread_cond_wait\fP function returns
+the following error codes on error:
+.RS
+.TP
+\fBEPERM\fP
+\fBmutex\fP is not locked.
+.RE
+.P
 The \fBpthread_cond_timedwait\fP function returns
 the following error codes on error:
 .RS
 .TP
+\fBEPERM\fP
+\fBmutex\fP is not locked.
+.TP
 \fBETIMEDOUT\fP
 The condition variable was not signaled
 until the timeout specified by \fIabstime\fP.

[-- Attachment #3: wait2.c --]
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/*
clang -o wait2 wait2.c -Wall -g;./wait2&p=$!;sleep 0.1;kill -USR1 $p;wait $p
[1] 3574450
signal
110=Connection timed out
[1]+  Exit 1                  ./wait2
*/
#define _GNU_SOURCE
#include <pthread.h>
#include <assert.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <signal.h>
#include <sys/time.h>
static void sig(int signo) {
  puts("signal");
}
int main(void) {
  setbuf(stdout,NULL);
  struct sigaction sa;
  memset(&sa,0,sizeof(sa));
  sa.sa_handler=sig;
  int err;
  err=sigaction(SIGUSR1,&sa,NULL);
  assert(!err);
//  pthread_mutex_t mut = PTHREAD_MUTEX_INITIALIZER; // not reproducible
  pthread_mutex_t mut = PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP;
  pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
  err=pthread_mutex_lock(&mut);
  assert(!err);
  struct timeval tv;
  err=gettimeofday(&tv,NULL/*tz*/);
  assert(!err);
  struct timespec ts;
  ts.tv_sec=tv.tv_sec;
  ts.tv_nsec=tv.tv_usec*1000;
  ts.tv_sec++;
  err=pthread_cond_timedwait(&cond, &mut, &ts);
  if (err) {
    printf("%d=%s\n",err,strerror(err));
    return 1;
  }
  return 0;
}

Re: [patch] pthread_cond_wait and pthread_cond_timedwait can also return EPERMignalignal

[Florian Weimer]

* Jan Kratochvil:

> On Thu, 10 Oct 2024 18:32:51 +0800, Florian Weimer wrote:
>> * Jan Kratochvil:
>> 
>> > +\fBEINTR\fP
>> > +\fBpthread_cond_wait\fP was interrupted by a signal.
>> > +.RE
>> 
>> POSIX specifically disallows returning EINTR.  Applications cannot
>> expect that pthread_cond_wait returns upon delivery of a signal.  Such
>> a return is only possible due to the general allowance for spurious
>> wakeups, and must result in a zero result.
>
> OK, I agree when I tried that. So I have removed this part.
>
> But then I believe the EINTR presence at pthread_cond_timedwait documentation
> is also wrong (I did not change that in this patch) as I could not reproduce
> the EINTR (attached).

Indeed, POSIX disallows EINTR for all three wait functions.

[patchv3] pthread_cond_wait and pthread_cond_timedwait can also return EPERM

[Jan Kratochvil]

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On Thu, 10 Oct 2024 20:25:56 +0800, Florian Weimer wrote:
> Indeed, POSIX disallows EINTR for all three wait functions.

Fixed.


Jan

Signed-off-by: Jan Kratochvil <jan@jankratochvil.net>
Reviewed-by: Florian Weimer <fw@deneb.enyo.de>

[-- Attachment #2: pthread_cond_init.3.patch --]
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diff --git a/man/man3/pthread_cond_init.3 b/man/man3/pthread_cond_init.3
index 42e7eac..df1f631 100644
--- a/man/man3/pthread_cond_init.3
+++ b/man/man3/pthread_cond_init.3
@@ -141,22 +141,28 @@ and a non-zero error code on error.
 .
 .SH ERRORS
 \fBpthread_cond_init\fP,
-\fBpthread_cond_signal\fP,
-\fBpthread_cond_broadcast\fP,
-and \fBpthread_cond_wait\fP
+\fBpthread_cond_signal\fP
+and \fBpthread_cond_broadcast\fP,
 never return an error code.
 .P
+The \fBpthread_cond_wait\fP function returns
+the following error codes on error:
+.RS
+.TP
+\fBEPERM\fP
+\fBmutex\fP is not locked.
+.RE
+.P
 The \fBpthread_cond_timedwait\fP function returns
 the following error codes on error:
 .RS
 .TP
+\fBEPERM\fP
+\fBmutex\fP is not locked.
+.TP
 \fBETIMEDOUT\fP
 The condition variable was not signaled
 until the timeout specified by \fIabstime\fP.
-.TP
-\fBEINTR\fP
-\fBpthread_cond_timedwait\fP was interrupted by a signal.
-.RE
 .P
 The \fBpthread_cond_destroy\fP function returns
 the following error code on error:

Re: [patchv3] pthread_cond_wait and pthread_cond_timedwait can also return EPERM

[Alejandro Colomar]

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Hi Jan,

On Thu, Oct 10, 2024 at 08:39:20PM +0800, Jan Kratochvil wrote:
> On Thu, 10 Oct 2024 20:25:56 +0800, Florian Weimer wrote:
> > Indeed, POSIX disallows EINTR for all three wait functions.
> 
> Fixed.
> 
> 
> Jan
> 
> Signed-off-by: Jan Kratochvil <jan@jankratochvil.net>
> Reviewed-by: Florian Weimer <fw@deneb.enyo.de>

Patch applied.  Thank you both!

Have a lovely day!
Alex

> diff --git a/man/man3/pthread_cond_init.3 b/man/man3/pthread_cond_init.3
> index 42e7eac..df1f631 100644
> --- a/man/man3/pthread_cond_init.3
> +++ b/man/man3/pthread_cond_init.3
> @@ -141,22 +141,28 @@ and a non-zero error code on error.
>  .
>  .SH ERRORS
>  \fBpthread_cond_init\fP,
> -\fBpthread_cond_signal\fP,
> -\fBpthread_cond_broadcast\fP,
> -and \fBpthread_cond_wait\fP
> +\fBpthread_cond_signal\fP
> +and \fBpthread_cond_broadcast\fP,
>  never return an error code.
>  .P
> +The \fBpthread_cond_wait\fP function returns
> +the following error codes on error:
> +.RS
> +.TP
> +\fBEPERM\fP
> +\fBmutex\fP is not locked.
> +.RE
> +.P
>  The \fBpthread_cond_timedwait\fP function returns
>  the following error codes on error:
>  .RS
>  .TP
> +\fBEPERM\fP
> +\fBmutex\fP is not locked.
> +.TP
>  \fBETIMEDOUT\fP
>  The condition variable was not signaled
>  until the timeout specified by \fIabstime\fP.
> -.TP
> -\fBEINTR\fP
> -\fBpthread_cond_timedwait\fP was interrupted by a signal.
> -.RE
>  .P
>  The \fBpthread_cond_destroy\fP function returns
>  the following error code on error:


-- 
<https://www.alejandro-colomar.es/>

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Re: [patchv3] pthread_cond_wait and pthread_cond_timedwait can also return EPERM

[Alejandro Colomar]

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Hi Jan, Florian,

On Fri, Nov 01, 2024 at 02:10:16PM +0100, Alejandro Colomar wrote:
> Hi Jan,
> 
> On Thu, Oct 10, 2024 at 08:39:20PM +0800, Jan Kratochvil wrote:
> > On Thu, 10 Oct 2024 20:25:56 +0800, Florian Weimer wrote:
> > > Indeed, POSIX disallows EINTR for all three wait functions.
> > 
> > Fixed.
> > 
> > 
> > Jan
> > 
> > Signed-off-by: Jan Kratochvil <jan@jankratochvil.net>
> > Reviewed-by: Florian Weimer <fw@deneb.enyo.de>
> 
> Patch applied.  Thank you both!

Sorry, no; I've removed the patch.  It does two things, but I prefer if
you send two patches, each of which changes one thing, and please
provide a more detailed commit message.  Thanks.

Cheers,
Alex

> 
> Have a lovely day!
> Alex
> 
> > diff --git a/man/man3/pthread_cond_init.3 b/man/man3/pthread_cond_init.3
> > index 42e7eac..df1f631 100644
> > --- a/man/man3/pthread_cond_init.3
> > +++ b/man/man3/pthread_cond_init.3
> > @@ -141,22 +141,28 @@ and a non-zero error code on error.
> >  .
> >  .SH ERRORS
> >  \fBpthread_cond_init\fP,
> > -\fBpthread_cond_signal\fP,
> > -\fBpthread_cond_broadcast\fP,
> > -and \fBpthread_cond_wait\fP
> > +\fBpthread_cond_signal\fP
> > +and \fBpthread_cond_broadcast\fP,
> >  never return an error code.
> >  .P
> > +The \fBpthread_cond_wait\fP function returns
> > +the following error codes on error:
> > +.RS
> > +.TP
> > +\fBEPERM\fP
> > +\fBmutex\fP is not locked.
> > +.RE
> > +.P
> >  The \fBpthread_cond_timedwait\fP function returns
> >  the following error codes on error:
> >  .RS
> >  .TP
> > +\fBEPERM\fP
> > +\fBmutex\fP is not locked.
> > +.TP
> >  \fBETIMEDOUT\fP
> >  The condition variable was not signaled
> >  until the timeout specified by \fIabstime\fP.
> > -.TP
> > -\fBEINTR\fP
> > -\fBpthread_cond_timedwait\fP was interrupted by a signal.
> > -.RE
> >  .P
> >  The \fBpthread_cond_destroy\fP function returns
> >  the following error code on error:
> 
> 
> -- 
> <https://www.alejandro-colomar.es/>



-- 
<https://www.alejandro-colomar.es/>

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