Re: [PATCH] drivers/crypto: Use RCU_INIT_POINTER(x, NULL) in nx/nx-842.c
On Mon, Mar 24, 2014 at 01:01:04AM +0530, Monam Agarwal wrote: This patch replaces rcu_assign_pointer(x, NULL) with RCU_INIT_POINTER(x, NULL) The rcu_assign_pointer() ensures that the initialization of a structure is carried out before storing a pointer to that structure. And in the case of the NULL pointer, there is no structure to initialize. So, rcu_assign_pointer(p, NULL) can be safely converted to RCU_INIT_POINTER(p, NULL) Signed-off-by: Monam Agarwal monamagarwal...@gmail.com --- drivers/crypto/nx/nx-842.c |4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/crypto/nx/nx-842.c b/drivers/crypto/nx/nx-842.c index 1e5481d..c4fcbf4 100644 --- a/drivers/crypto/nx/nx-842.c +++ b/drivers/crypto/nx/nx-842.c @@ -1234,7 +1234,7 @@ static int __exit nx842_remove(struct vio_dev *viodev) old_devdata = rcu_dereference_check(devdata, lockdep_is_held(devdata_mutex)); of_reconfig_notifier_unregister(nx842_of_nb); - rcu_assign_pointer(devdata, NULL); + RCU_INIT_POINTER(devdata, NULL); spin_unlock_irqrestore(devdata_mutex, flags); synchronize_rcu(); dev_set_drvdata(viodev-dev, NULL); @@ -1285,7 +1285,7 @@ static void __exit nx842_exit(void) spin_lock_irqsave(devdata_mutex, flags); old_devdata = rcu_dereference_check(devdata, lockdep_is_held(devdata_mutex)); - rcu_assign_pointer(devdata, NULL); + RCU_INIT_POINTER(devdata, NULL); spin_unlock_irqrestore(devdata_mutex, flags); synchronize_rcu(); if (old_devdata) This really does't seem right. rcu_assign_pointer users ACCESS_ONCE to protect against multiple loads that allow for concurrent read/write use with parallel rcu_dereference calls, whereas RCU_INIT_POINTER does not. It also just doesn't look right. We've already initalized the pointerin nx842_init, we don't need to re-initalize it here, we need to assign it to NULL. Neil -- 1.7.9.5 -- To unsubscribe from this list: send the line unsubscribe linux-crypto in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line unsubscribe linux-crypto in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH] drivers/crypto: Use RCU_INIT_POINTER(x, NULL) in nx/nx-842.c
On 24/03/14 12:16, Neil Horman wrote: On Mon, Mar 24, 2014 at 01:01:04AM +0530, Monam Agarwal wrote: This patch replaces rcu_assign_pointer(x, NULL) with RCU_INIT_POINTER(x, NULL) The rcu_assign_pointer() ensures that the initialization of a structure is carried out before storing a pointer to that structure. And in the case of the NULL pointer, there is no structure to initialize. So, rcu_assign_pointer(p, NULL) can be safely converted to RCU_INIT_POINTER(p, NULL) Signed-off-by: Monam Agarwal monamagarwal...@gmail.com --- drivers/crypto/nx/nx-842.c |4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/crypto/nx/nx-842.c b/drivers/crypto/nx/nx-842.c index 1e5481d..c4fcbf4 100644 --- a/drivers/crypto/nx/nx-842.c +++ b/drivers/crypto/nx/nx-842.c @@ -1234,7 +1234,7 @@ static int __exit nx842_remove(struct vio_dev *viodev) old_devdata = rcu_dereference_check(devdata, lockdep_is_held(devdata_mutex)); of_reconfig_notifier_unregister(nx842_of_nb); - rcu_assign_pointer(devdata, NULL); + RCU_INIT_POINTER(devdata, NULL); spin_unlock_irqrestore(devdata_mutex, flags); synchronize_rcu(); dev_set_drvdata(viodev-dev, NULL); @@ -1285,7 +1285,7 @@ static void __exit nx842_exit(void) spin_lock_irqsave(devdata_mutex, flags); old_devdata = rcu_dereference_check(devdata, lockdep_is_held(devdata_mutex)); - rcu_assign_pointer(devdata, NULL); + RCU_INIT_POINTER(devdata, NULL); spin_unlock_irqrestore(devdata_mutex, flags); synchronize_rcu(); if (old_devdata) This really does't seem right. rcu_assign_pointer users ACCESS_ONCE to protect against multiple loads that allow for concurrent read/write use with parallel rcu_dereference calls, whereas RCU_INIT_POINTER does not. It also just doesn't look right. We've already initalized the pointerin nx842_init, we don't need to re-initalize it here, we need to assign it to NULL. I was being cautious as well, but Paul gave me an explanation [1] Hope it helps you as well ;-) But I think I also saw a patch that modifies rcu_assign_pointer to handle NULL assignment. Don't recall the thread. Regards, Arend [1] http://mid.gmane.org/20140320150601.gk4...@linux.vnet.ibm.com Neil -- 1.7.9.5 -- To unsubscribe from this list: send the line unsubscribe linux-crypto in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ -- To unsubscribe from this list: send the line unsubscribe linux-crypto in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
[PATCH] drivers/crypto: Use RCU_INIT_POINTER(x, NULL) in nx/nx-842.c
This patch replaces rcu_assign_pointer(x, NULL) with RCU_INIT_POINTER(x, NULL) The rcu_assign_pointer() ensures that the initialization of a structure is carried out before storing a pointer to that structure. And in the case of the NULL pointer, there is no structure to initialize. So, rcu_assign_pointer(p, NULL) can be safely converted to RCU_INIT_POINTER(p, NULL) Signed-off-by: Monam Agarwal monamagarwal...@gmail.com --- drivers/crypto/nx/nx-842.c |4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/crypto/nx/nx-842.c b/drivers/crypto/nx/nx-842.c index 1e5481d..c4fcbf4 100644 --- a/drivers/crypto/nx/nx-842.c +++ b/drivers/crypto/nx/nx-842.c @@ -1234,7 +1234,7 @@ static int __exit nx842_remove(struct vio_dev *viodev) old_devdata = rcu_dereference_check(devdata, lockdep_is_held(devdata_mutex)); of_reconfig_notifier_unregister(nx842_of_nb); - rcu_assign_pointer(devdata, NULL); + RCU_INIT_POINTER(devdata, NULL); spin_unlock_irqrestore(devdata_mutex, flags); synchronize_rcu(); dev_set_drvdata(viodev-dev, NULL); @@ -1285,7 +1285,7 @@ static void __exit nx842_exit(void) spin_lock_irqsave(devdata_mutex, flags); old_devdata = rcu_dereference_check(devdata, lockdep_is_held(devdata_mutex)); - rcu_assign_pointer(devdata, NULL); + RCU_INIT_POINTER(devdata, NULL); spin_unlock_irqrestore(devdata_mutex, flags); synchronize_rcu(); if (old_devdata) -- 1.7.9.5 -- To unsubscribe from this list: send the line unsubscribe linux-crypto in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
[PATCH] drivers/crypto: Use RCU_INIT_POINTER(x, NULL) in nx/nx-842.c
This patch replaces rcu_assign_pointer(x, NULL) with RCU_INIT_POINTER(x, NULL) The rcu_assign_pointer() ensures that the initialization of a structure is carried out before storing a pointer to that structure. And in the case of the NULL pointer, there is no structure to initialize. So, rcu_assign_pointer(p, NULL) can be safely converted to RCU_INIT_POINTER(p, NULL) Signed-off-by: Monam Agarwal monamagarwal...@gmail.com --- drivers/crypto/nx/nx-842.c |4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/crypto/nx/nx-842.c b/drivers/crypto/nx/nx-842.c index 1e5481d..c4fcbf4 100644 --- a/drivers/crypto/nx/nx-842.c +++ b/drivers/crypto/nx/nx-842.c @@ -1234,7 +1234,7 @@ static int __exit nx842_remove(struct vio_dev *viodev) old_devdata = rcu_dereference_check(devdata, lockdep_is_held(devdata_mutex)); of_reconfig_notifier_unregister(nx842_of_nb); - rcu_assign_pointer(devdata, NULL); + RCU_INIT_POINTER(devdata, NULL); spin_unlock_irqrestore(devdata_mutex, flags); synchronize_rcu(); dev_set_drvdata(viodev-dev, NULL); @@ -1285,7 +1285,7 @@ static void __exit nx842_exit(void) spin_lock_irqsave(devdata_mutex, flags); old_devdata = rcu_dereference_check(devdata, lockdep_is_held(devdata_mutex)); - rcu_assign_pointer(devdata, NULL); + RCU_INIT_POINTER(devdata, NULL); spin_unlock_irqrestore(devdata_mutex, flags); synchronize_rcu(); if (old_devdata) -- 1.7.9.5 -- To unsubscribe from this list: send the line unsubscribe linux-crypto in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
[PATCH] drivers/crypto: Use RCU_INIT_POINTER(x, NULL) in nx/nx-842.c
This patch replaces rcu_assign_pointer(x, NULL) with RCU_INIT_POINTER(x, NULL) The rcu_assign_pointer() ensures that the initialization of a structure is carried out before storing a pointer to that structure. And in the case of the NULL pointer, there is no structure to initialize. So, rcu_assign_pointer(p, NULL) can be safely converted to RCU_INIT_POINTER(p, NULL) Signed-off-by: Monam Agarwal monamagarwal...@gmail.com --- drivers/crypto/nx/nx-842.c |4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/crypto/nx/nx-842.c b/drivers/crypto/nx/nx-842.c index 1e5481d..c4fcbf4 100644 --- a/drivers/crypto/nx/nx-842.c +++ b/drivers/crypto/nx/nx-842.c @@ -1234,7 +1234,7 @@ static int __exit nx842_remove(struct vio_dev *viodev) old_devdata = rcu_dereference_check(devdata, lockdep_is_held(devdata_mutex)); of_reconfig_notifier_unregister(nx842_of_nb); - rcu_assign_pointer(devdata, NULL); + RCU_INIT_POINTER(devdata, NULL); spin_unlock_irqrestore(devdata_mutex, flags); synchronize_rcu(); dev_set_drvdata(viodev-dev, NULL); @@ -1285,7 +1285,7 @@ static void __exit nx842_exit(void) spin_lock_irqsave(devdata_mutex, flags); old_devdata = rcu_dereference_check(devdata, lockdep_is_held(devdata_mutex)); - rcu_assign_pointer(devdata, NULL); + RCU_INIT_POINTER(devdata, NULL); spin_unlock_irqrestore(devdata_mutex, flags); synchronize_rcu(); if (old_devdata) -- 1.7.9.5 -- To unsubscribe from this list: send the line unsubscribe linux-crypto in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
