Re: [rfc][patch] futex: restartable futex_wait?
On Fri, 2007-03-09 at 13:24 +0100, Nick Piggin wrote: > > > > 'time' here is relative, so the restarted syscall will do a /full/ wait > > > > again. > > > > > > But it has been modified by schedule_timeout? > > > > But this does not change the syscall registers, so it is restarted in > > the same way. We need a new futex OP for this, which takes absolute time > > like the PI futex op does. > > Forgive me if I'm missing something here, but I'm using the restart block > and saving the updated value of time in ->arg2, and using that as the new > time parameter passed into futex_wait from futex_wait_restart. Oops. I went into confusion mode. You are right, the restart block keeps that. tglx - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [rfc][patch] futex: restartable futex_wait?
On Fri, Mar 09, 2007 at 10:38:35AM +0100, Thomas Gleixner wrote: > On Fri, 2007-03-09 at 06:10 +0100, Nick Piggin wrote: > > > i think that's quite right. I'm wondering why this never came up before? > > > But your fix is not complete i think: > > > > > > > + restart->arg2 = time; > > > > + return -ERESTART_RESTARTBLOCK; > > > > + } > > > > > > 'time' here is relative, so the restarted syscall will do a /full/ wait > > > again. > > > > But it has been modified by schedule_timeout? > > But this does not change the syscall registers, so it is restarted in > the same way. We need a new futex OP for this, which takes absolute time > like the PI futex op does. Forgive me if I'm missing something here, but I'm using the restart block and saving the updated value of time in ->arg2, and using that as the new time parameter passed into futex_wait from futex_wait_restart. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [rfc][patch] futex: restartable futex_wait?
On Fri, 2007-03-09 at 06:10 +0100, Nick Piggin wrote: > > i think that's quite right. I'm wondering why this never came up before? > > But your fix is not complete i think: > > > > > + restart->arg2 = time; > > > + return -ERESTART_RESTARTBLOCK; > > > + } > > > > 'time' here is relative, so the restarted syscall will do a /full/ wait > > again. > > But it has been modified by schedule_timeout? But this does not change the syscall registers, so it is restarted in the same way. We need a new futex OP for this, which takes absolute time like the PI futex op does. tglx - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [rfc][patch] futex: restartable futex_wait?
On Fri, 2007-03-09 at 06:10 +0100, Nick Piggin wrote: i think that's quite right. I'm wondering why this never came up before? But your fix is not complete i think: + restart-arg2 = time; + return -ERESTART_RESTARTBLOCK; + } 'time' here is relative, so the restarted syscall will do a /full/ wait again. But it has been modified by schedule_timeout? But this does not change the syscall registers, so it is restarted in the same way. We need a new futex OP for this, which takes absolute time like the PI futex op does. tglx - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [rfc][patch] futex: restartable futex_wait?
On Fri, Mar 09, 2007 at 10:38:35AM +0100, Thomas Gleixner wrote: On Fri, 2007-03-09 at 06:10 +0100, Nick Piggin wrote: i think that's quite right. I'm wondering why this never came up before? But your fix is not complete i think: + restart-arg2 = time; + return -ERESTART_RESTARTBLOCK; + } 'time' here is relative, so the restarted syscall will do a /full/ wait again. But it has been modified by schedule_timeout? But this does not change the syscall registers, so it is restarted in the same way. We need a new futex OP for this, which takes absolute time like the PI futex op does. Forgive me if I'm missing something here, but I'm using the restart block and saving the updated value of time in -arg2, and using that as the new time parameter passed into futex_wait from futex_wait_restart. - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [rfc][patch] futex: restartable futex_wait?
On Fri, 2007-03-09 at 13:24 +0100, Nick Piggin wrote: 'time' here is relative, so the restarted syscall will do a /full/ wait again. But it has been modified by schedule_timeout? But this does not change the syscall registers, so it is restarted in the same way. We need a new futex OP for this, which takes absolute time like the PI futex op does. Forgive me if I'm missing something here, but I'm using the restart block and saving the updated value of time in -arg2, and using that as the new time parameter passed into futex_wait from futex_wait_restart. Oops. I went into confusion mode. You are right, the restart block keeps that. tglx - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [rfc][patch] futex: restartable futex_wait?
On Fri, Mar 09, 2007 at 12:02:31AM +0100, Thomas Gleixner wrote: > On Thu, 2007-03-08 at 18:29 +0100, Ingo Molnar wrote: > > * Nick Piggin <[EMAIL PROTECTED]> wrote: > > > > > Hi Ingo, > > > > > > I'm seeing an LTP test fail for ltp test sigaction_16_24. Basically, > > > it tests whether the SA_RESTART flag works for the sem_wait operation. > > Not sure, whether the testcase is correct or not. See below > > > > I see sem_wait is implemented with futex_wait, so I wonder whether we > > > can make it restartable? Am I going about it the right way? (Seems to > > > fix the testcase here). > > > > i think that's quite right. I'm wondering why this never came up before? > > But your fix is not complete i think: > > > > > + restart->arg2 = time; > > > + return -ERESTART_RESTARTBLOCK; > > > + } > > > > 'time' here is relative, so the restarted syscall will do a /full/ wait > > again. > > > > maybe we should rather convert futex timed-waits to hrtimers? Thomas? > > The problem is that the original API is based on relative time and > therefor can not be changed. > > sem_wait returns -EINTR to the application when it is interrupted, while > pthread_mutex_lock does not. But this still means sem_wait should restart if SA_RESTART is set, right? And pthread_mutex_lock could be implemented to not return -EINTR, even if futex_wait does, couldn't it? (I guess it probably already is, considering that futex_wait alsready returns -EINTR). > > http://www.opengroup.org/onlinepubs/009695399/functions/sem_wait.html > > http://www.opengroup.org/onlinepubs/009695399/functions/pthread_mutex_lock.html > > We need to create a seperate op for the futex - just like the pi_futex > and use absolute time there too. > > tglx > - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [rfc][patch] futex: restartable futex_wait?
On Thu, Mar 08, 2007 at 06:29:02PM +0100, Ingo Molnar wrote: > > * Nick Piggin <[EMAIL PROTECTED]> wrote: > > > Hi Ingo, > > > > I'm seeing an LTP test fail for ltp test sigaction_16_24. Basically, > > it tests whether the SA_RESTART flag works for the sem_wait operation. > > > > I see sem_wait is implemented with futex_wait, so I wonder whether we > > can make it restartable? Am I going about it the right way? (Seems to > > fix the testcase here). > > i think that's quite right. I'm wondering why this never came up before? > But your fix is not complete i think: > > > + restart->arg2 = time; > > + return -ERESTART_RESTARTBLOCK; > > + } > > 'time' here is relative, so the restarted syscall will do a /full/ wait > again. But it has been modified by schedule_timeout? - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [rfc][patch] futex: restartable futex_wait?
On Thu, 2007-03-08 at 18:29 +0100, Ingo Molnar wrote: > * Nick Piggin <[EMAIL PROTECTED]> wrote: > > > Hi Ingo, > > > > I'm seeing an LTP test fail for ltp test sigaction_16_24. Basically, > > it tests whether the SA_RESTART flag works for the sem_wait operation. Not sure, whether the testcase is correct or not. See below > > I see sem_wait is implemented with futex_wait, so I wonder whether we > > can make it restartable? Am I going about it the right way? (Seems to > > fix the testcase here). > > i think that's quite right. I'm wondering why this never came up before? > But your fix is not complete i think: > > > + restart->arg2 = time; > > + return -ERESTART_RESTARTBLOCK; > > + } > > 'time' here is relative, so the restarted syscall will do a /full/ wait > again. > > maybe we should rather convert futex timed-waits to hrtimers? Thomas? The problem is that the original API is based on relative time and therefor can not be changed. sem_wait returns -EINTR to the application when it is interrupted, while pthread_mutex_lock does not. http://www.opengroup.org/onlinepubs/009695399/functions/sem_wait.html http://www.opengroup.org/onlinepubs/009695399/functions/pthread_mutex_lock.html We need to create a seperate op for the futex - just like the pi_futex and use absolute time there too. tglx - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [rfc][patch] futex: restartable futex_wait?
* Nick Piggin <[EMAIL PROTECTED]> wrote: > Hi Ingo, > > I'm seeing an LTP test fail for ltp test sigaction_16_24. Basically, > it tests whether the SA_RESTART flag works for the sem_wait operation. > > I see sem_wait is implemented with futex_wait, so I wonder whether we > can make it restartable? Am I going about it the right way? (Seems to > fix the testcase here). i think that's quite right. I'm wondering why this never came up before? But your fix is not complete i think: > + restart->arg2 = time; > + return -ERESTART_RESTARTBLOCK; > + } 'time' here is relative, so the restarted syscall will do a /full/ wait again. maybe we should rather convert futex timed-waits to hrtimers? Thomas? Ingo - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [rfc][patch] futex: restartable futex_wait?
* Nick Piggin [EMAIL PROTECTED] wrote: Hi Ingo, I'm seeing an LTP test fail for ltp test sigaction_16_24. Basically, it tests whether the SA_RESTART flag works for the sem_wait operation. I see sem_wait is implemented with futex_wait, so I wonder whether we can make it restartable? Am I going about it the right way? (Seems to fix the testcase here). i think that's quite right. I'm wondering why this never came up before? But your fix is not complete i think: + restart-arg2 = time; + return -ERESTART_RESTARTBLOCK; + } 'time' here is relative, so the restarted syscall will do a /full/ wait again. maybe we should rather convert futex timed-waits to hrtimers? Thomas? Ingo - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [rfc][patch] futex: restartable futex_wait?
On Thu, 2007-03-08 at 18:29 +0100, Ingo Molnar wrote: * Nick Piggin [EMAIL PROTECTED] wrote: Hi Ingo, I'm seeing an LTP test fail for ltp test sigaction_16_24. Basically, it tests whether the SA_RESTART flag works for the sem_wait operation. Not sure, whether the testcase is correct or not. See below I see sem_wait is implemented with futex_wait, so I wonder whether we can make it restartable? Am I going about it the right way? (Seems to fix the testcase here). i think that's quite right. I'm wondering why this never came up before? But your fix is not complete i think: + restart-arg2 = time; + return -ERESTART_RESTARTBLOCK; + } 'time' here is relative, so the restarted syscall will do a /full/ wait again. maybe we should rather convert futex timed-waits to hrtimers? Thomas? The problem is that the original API is based on relative time and therefor can not be changed. sem_wait returns -EINTR to the application when it is interrupted, while pthread_mutex_lock does not. http://www.opengroup.org/onlinepubs/009695399/functions/sem_wait.html http://www.opengroup.org/onlinepubs/009695399/functions/pthread_mutex_lock.html We need to create a seperate op for the futex - just like the pi_futex and use absolute time there too. tglx - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [rfc][patch] futex: restartable futex_wait?
On Thu, Mar 08, 2007 at 06:29:02PM +0100, Ingo Molnar wrote: * Nick Piggin [EMAIL PROTECTED] wrote: Hi Ingo, I'm seeing an LTP test fail for ltp test sigaction_16_24. Basically, it tests whether the SA_RESTART flag works for the sem_wait operation. I see sem_wait is implemented with futex_wait, so I wonder whether we can make it restartable? Am I going about it the right way? (Seems to fix the testcase here). i think that's quite right. I'm wondering why this never came up before? But your fix is not complete i think: + restart-arg2 = time; + return -ERESTART_RESTARTBLOCK; + } 'time' here is relative, so the restarted syscall will do a /full/ wait again. But it has been modified by schedule_timeout? - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [rfc][patch] futex: restartable futex_wait?
On Fri, Mar 09, 2007 at 12:02:31AM +0100, Thomas Gleixner wrote: On Thu, 2007-03-08 at 18:29 +0100, Ingo Molnar wrote: * Nick Piggin [EMAIL PROTECTED] wrote: Hi Ingo, I'm seeing an LTP test fail for ltp test sigaction_16_24. Basically, it tests whether the SA_RESTART flag works for the sem_wait operation. Not sure, whether the testcase is correct or not. See below I see sem_wait is implemented with futex_wait, so I wonder whether we can make it restartable? Am I going about it the right way? (Seems to fix the testcase here). i think that's quite right. I'm wondering why this never came up before? But your fix is not complete i think: + restart-arg2 = time; + return -ERESTART_RESTARTBLOCK; + } 'time' here is relative, so the restarted syscall will do a /full/ wait again. maybe we should rather convert futex timed-waits to hrtimers? Thomas? The problem is that the original API is based on relative time and therefor can not be changed. sem_wait returns -EINTR to the application when it is interrupted, while pthread_mutex_lock does not. But this still means sem_wait should restart if SA_RESTART is set, right? And pthread_mutex_lock could be implemented to not return -EINTR, even if futex_wait does, couldn't it? (I guess it probably already is, considering that futex_wait alsready returns -EINTR). http://www.opengroup.org/onlinepubs/009695399/functions/sem_wait.html http://www.opengroup.org/onlinepubs/009695399/functions/pthread_mutex_lock.html We need to create a seperate op for the futex - just like the pi_futex and use absolute time there too. tglx - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
