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Re: [libvirt] [PATCH] build: avoid non-portable cast of pthread_t



Hi Eric,
On Thu, May 02, 2013 at 03:58:23PM -0600, Eric Blake wrote:
> POSIX says pthread_t is opaque.  We can't guarantee if it is scaler
> or a pointer, nor what size it is; and BSD differs from Linux.
> We've also had reports of gcc complaining on attempts to cast it,
> if we use a cast to the wrong type (for example, pointers have to be
> cast to void* or intptr_t before being narrowed; while casting a
> function return of pthread_t to void* triggers another warning).
> 
> Give up on casts, and use unions to get at decent bits instead.  And
> rather than futz around with figuring which 32 bits of a potentially
> 64-bit pointer are most likely to be unique, convert the rest of
> the code base to use 64-bit values when using a debug id.
> 
> Based on a report by Guido Günther against kFreeBSD, but with a
> fix that doesn't regress commit 4d970fd29 for FreeBSD.

Works on kFreeBSD here, thanks.
 -- Guido

> 
> * src/util/virthreadpthread.c (virThreadSelfID, virThreadID): Use
> union to get at a decent bit representation of thread_t bits.
> * src/util/virthread.h (virThreadSelfID, virThreadID): Alter
> signature.
> * src/util/virthreadwin32.c (virThreadSelfID, virThreadID):
> Likewise.
> * src/qemu/qemu_domain.h (qemuDomainJobObj): Alter type of owner.
> * src/qemu/qemu_domain.c (qemuDomainObjTransferJob)
> (qemuDomainObjSetJobPhase, qemuDomainObjReleaseAsyncJob)
> (qemuDomainObjBeginNestedJob, qemuDomainObjBeginJobInternal): Fix
> clients.
> * src/util/virlog.c (virLogFormatString): Likewise.
> * src/util/vireventpoll.c (virEventPollInterruptLocked):
> Likewise.
> 
> Signed-off-by: Eric Blake <eblake redhat com>
> ---
> 
> This one needs a review.
> 
> I've tested this on Fedora 18 and FreeBSD 8.2; I also ran it through
> the mingw64 cross-compiler on Fedora (thanks to autobuild.sh), without
> grief.  But I don't have a kFreeBSD system handy, which was the
> original source of the compilation complaint.
> 
>  src/qemu/qemu_domain.c      | 12 ++++++------
>  src/qemu/qemu_domain.h      |  4 ++--
>  src/util/vireventpoll.c     |  4 ++--
>  src/util/virlog.c           |  6 +++---
>  src/util/virthread.h        |  6 +++---
>  src/util/virthreadpthread.c | 33 ++++++++++++++++++++++-----------
>  src/util/virthreadwin32.c   | 12 ++++++------
>  7 files changed, 44 insertions(+), 33 deletions(-)
> 
> diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
> index 47edfba..bfc57e5 100644
> --- a/src/qemu/qemu_domain.c
> +++ b/src/qemu/qemu_domain.c
> @@ -187,7 +187,7 @@ qemuDomainObjTransferJob(virDomainObjPtr obj)
>  {
>      qemuDomainObjPrivatePtr priv = obj->privateData;
> 
> -    VIR_DEBUG("Changing job owner from %d to %d",
> +    VIR_DEBUG("Changing job owner from %lld to %lld",
>                priv->job.owner, virThreadSelfID());
>      priv->job.owner = virThreadSelfID();
>  }
> @@ -846,7 +846,7 @@ qemuDomainObjSetJobPhase(virQEMUDriverPtr driver,
>                           int phase)
>  {
>      qemuDomainObjPrivatePtr priv = obj->privateData;
> -    int me = virThreadSelfID();
> +    unsigned long long int me = virThreadSelfID();
> 
>      if (!priv->job.asyncJob)
>          return;
> @@ -856,7 +856,7 @@ qemuDomainObjSetJobPhase(virQEMUDriverPtr driver,
>                qemuDomainAsyncJobPhaseToString(priv->job.asyncJob, phase));
> 
>      if (priv->job.asyncOwner && me != priv->job.asyncOwner) {
> -        VIR_WARN("'%s' async job is owned by thread %d",
> +        VIR_WARN("'%s' async job is owned by thread %lld",
>                   qemuDomainAsyncJobTypeToString(priv->job.asyncJob),
>                   priv->job.asyncOwner);
>      }
> @@ -898,7 +898,7 @@ qemuDomainObjReleaseAsyncJob(virDomainObjPtr obj)
>                qemuDomainAsyncJobTypeToString(priv->job.asyncJob));
> 
>      if (priv->job.asyncOwner != virThreadSelfID()) {
> -        VIR_WARN("'%s' async job is owned by thread %d",
> +        VIR_WARN("'%s' async job is owned by thread %lld",
>                   qemuDomainAsyncJobTypeToString(priv->job.asyncJob),
>                   priv->job.asyncOwner);
>      }
> @@ -992,7 +992,7 @@ retry:
> 
>  error:
>      VIR_WARN("Cannot start job (%s, %s) for domain %s;"
> -             " current job is (%s, %s) owned by (%d, %d)",
> +             " current job is (%s, %s) owned by (%lld, %lld)",
>               qemuDomainJobTypeToString(job),
>               qemuDomainAsyncJobTypeToString(asyncJob),
>               obj->def->name,
> @@ -1056,7 +1056,7 @@ qemuDomainObjBeginNestedJob(virQEMUDriverPtr driver,
>      }
> 
>      if (priv->job.asyncOwner != virThreadSelfID()) {
> -        VIR_WARN("This thread doesn't seem to be the async job owner: %d",
> +        VIR_WARN("This thread doesn't seem to be the async job owner: %lld",
>                   priv->job.asyncOwner);
>      }
> 
> diff --git a/src/qemu/qemu_domain.h b/src/qemu/qemu_domain.h
> index da04377..7746ba9 100644
> --- a/src/qemu/qemu_domain.h
> +++ b/src/qemu/qemu_domain.h
> @@ -102,11 +102,11 @@ VIR_ENUM_DECL(qemuDomainAsyncJob)
>  struct qemuDomainJobObj {
>      virCond cond;                       /* Use to coordinate jobs */
>      enum qemuDomainJob active;          /* Currently running job */
> -    int owner;                          /* Thread which set current job */
> +    unsigned long long int owner;       /* Thread id which set current job */
> 
>      virCond asyncCond;                  /* Use to coordinate with async jobs */
>      enum qemuDomainAsyncJob asyncJob;   /* Currently active async job */
> -    int asyncOwner;                     /* Thread which set current async job */
> +    unsigned long long int asyncOwner;  /* Thread which set current async job */
>      int phase;                          /* Job phase (mainly for migrations) */
>      unsigned long long mask;            /* Jobs allowed during async job */
>      unsigned long long start;           /* When the async job started */
> diff --git a/src/util/vireventpoll.c b/src/util/vireventpoll.c
> index 5c6d31b..19add73 100644
> --- a/src/util/vireventpoll.c
> +++ b/src/util/vireventpoll.c
> @@ -1,7 +1,7 @@
>  /*
>   * vireventpoll.c: Poll based event loop for monitoring file handles
>   *
> - * Copyright (C) 2007, 2010-2012 Red Hat, Inc.
> + * Copyright (C) 2007, 2010-2013 Red Hat, Inc.
>   * Copyright (C) 2007 Daniel P. Berrange
>   *
>   * This library is free software; you can redistribute it and/or
> @@ -708,7 +708,7 @@ static int virEventPollInterruptLocked(void)
> 
>      if (!eventLoop.running ||
>          virThreadIsSelf(&eventLoop.leader)) {
> -        VIR_DEBUG("Skip interrupt, %d %d", eventLoop.running,
> +        VIR_DEBUG("Skip interrupt, %d %lld", eventLoop.running,
>                    virThreadID(&eventLoop.leader));
>          return 0;
>      }
> diff --git a/src/util/virlog.c b/src/util/virlog.c
> index bd47b38..b2e6458 100644
> --- a/src/util/virlog.c
> +++ b/src/util/virlog.c
> @@ -1,7 +1,7 @@
>  /*
>   * virlog.c: internal logging and debugging
>   *
> - * Copyright (C) 2008, 2010-2012 Red Hat, Inc.
> + * Copyright (C) 2008, 2010-2013 Red Hat, Inc.
>   *
>   * This library is free software; you can redistribute it and/or
>   * modify it under the terms of the GNU Lesser General Public
> @@ -708,11 +708,11 @@ virLogFormatString(char **msg,
>       * to just grep for it to find the right place.
>       */
>      if ((funcname != NULL)) {
> -        ret = virAsprintf(msg, "%d: %s : %s:%d : %s\n",
> +        ret = virAsprintf(msg, "%lld: %s : %s:%d : %s\n",
>                            virThreadSelfID(), virLogPriorityString(priority),
>                            funcname, linenr, str);
>      } else {
> -        ret = virAsprintf(msg, "%d: %s : %s\n",
> +        ret = virAsprintf(msg, "%lld: %s : %s\n",
>                            virThreadSelfID(), virLogPriorityString(priority),
>                            str);
>      }
> diff --git a/src/util/virthread.h b/src/util/virthread.h
> index ca1306a..447fe84 100644
> --- a/src/util/virthread.h
> +++ b/src/util/virthread.h
> @@ -1,7 +1,7 @@
>  /*
>   * virthread.h: basic thread synchronization primitives
>   *
> - * Copyright (C) 2009-2011 Red Hat, Inc.
> + * Copyright (C) 2009-2011, 2013 Red Hat, Inc.
>   *
>   * This library is free software; you can redistribute it and/or
>   * modify it under the terms of the GNU Lesser General Public
> @@ -63,8 +63,8 @@ void virThreadCancel(virThreadPtr thread);
>   * guaranteed to give unique values for distinct threads on all
>   * architectures, nor are the two functions guaranteed to give the same
>   * value for the same thread. */
> -int virThreadSelfID(void);
> -int virThreadID(virThreadPtr thread);
> +unsigned long long int virThreadSelfID(void);
> +unsigned long long int virThreadID(virThreadPtr thread);
> 
>  /* Static initialization of mutexes is not possible, so we instead
>   * provide for guaranteed one-time initialization via a callback
> diff --git a/src/util/virthreadpthread.c b/src/util/virthreadpthread.c
> index b42b333..20fa539 100644
> --- a/src/util/virthreadpthread.c
> +++ b/src/util/virthreadpthread.c
> @@ -1,7 +1,7 @@
>  /*
>   * virthreadpthread.c: basic thread synchronization primitives
>   *
> - * Copyright (C) 2009-2011 Red Hat, Inc.
> + * Copyright (C) 2009-2011, 2013 Red Hat, Inc.
>   *
>   * This library is free software; you can redistribute it and/or
>   * modify it under the terms of the GNU Lesser General Public
> @@ -210,25 +210,36 @@ bool virThreadIsSelf(virThreadPtr thread)
>      return pthread_equal(pthread_self(), thread->thread) ? true : false;
>  }
> 
> -/* For debugging use only; this result is not guaranteed unique on BSD
> - * systems when pthread_t is a 64-bit pointer.  */
> -int virThreadSelfID(void)
> +/* For debugging use only; this result is not guaranteed unique if
> + * pthread_t is larger than a 64-bit pointer, nor does it always match
> + * the pthread_self() id on Linux.  */
> +unsigned long long int virThreadSelfID(void)
>  {
>  #if defined(HAVE_SYS_SYSCALL_H) && defined(SYS_gettid)
>      pid_t tid;
>      tid = syscall(SYS_gettid);
> -    return (int)tid;
> +    return tid;
>  #else
> -    return (int)(intptr_t)(void *)pthread_self();
> +    union {
> +        unsigned long long int i;
> +        pthread_t t;
> +    } u;
> +    u.t = pthread_self();
> +    return u.i;
>  #endif
>  }
> 
> -/* For debugging use only; this result is not guaranteed unique on BSD
> - * systems when pthread_t is a 64-bit pointer, nor does it match the
> - * thread id of virThreadSelfID on Linux.  */
> -int virThreadID(virThreadPtr thread)
> +/* For debugging use only; this result is not guaranteed unique if
> + * pthread_t is larger than a 64-bit pointer, nor does it always match
> + * the thread id of virThreadSelfID on Linux.  */
> +unsigned long long int virThreadID(virThreadPtr thread)
>  {
> -    return (int)(uintptr_t)thread->thread;
> +    union {
> +        unsigned long long int i;
> +        pthread_t t;
> +    } u;
> +    u.t = thread->thread;
> +    return u.i;
>  }
> 
>  void virThreadJoin(virThreadPtr thread)
> diff --git a/src/util/virthreadwin32.c b/src/util/virthreadwin32.c
> index 4543ad8..10837d2 100644
> --- a/src/util/virthreadwin32.c
> +++ b/src/util/virthreadwin32.c
> @@ -1,7 +1,7 @@
>  /*
>   * virthreadwin32.c: basic thread synchronization primitives
>   *
> - * Copyright (C) 2009-2011 Red Hat, Inc.
> + * Copyright (C) 2009-2011, 2013 Red Hat, Inc.
>   *
>   * This library is free software; you can redistribute it and/or
>   * modify it under the terms of the GNU Lesser General Public
> @@ -334,14 +334,14 @@ bool virThreadIsSelf(virThreadPtr thread)
>      return self.thread == thread->thread ? true : false;
>  }
> 
> -/* For debugging use only; see comments in threads-pthread.c.  */
> -int virThreadSelfID(void)
> +/* For debugging use only; see comments in virthreadpthread.c.  */
> +unsigned long long int virThreadSelfID(void)
>  {
> -    return (int)GetCurrentThreadId();
> +    return GetCurrentThreadId();
>  }
> 
> -/* For debugging use only; see comments in threads-pthread.c.  */
> -int virThreadID(virThreadPtr thread)
> +/* For debugging use only; see comments in virthreadpthread.c.  */
> +unsigned long long int virThreadID(virThreadPtr thread)
>  {
>      return (intptr_t)thread->thread;
>  }
> -- 
> 1.8.1.4
> 


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