* [PATCH 0/2] TPM
@ 2008-08-30 3:05 Rajiv Andrade
2008-08-30 3:05 ` [PATCH 1/2] TPM: update char dev BKL pushdown Rajiv Andrade
2008-08-30 3:05 ` [PATCH 2/2] TPM: rcu locking Rajiv Andrade
0 siblings, 2 replies; 7+ messages in thread
From: Rajiv Andrade @ 2008-08-30 3:05 UTC (permalink / raw)
To: linux-kernel
Cc: Andrew Morton, James Morris, Paul McKenney, Peter Dolding,
Kenneth Goldman, Debora Velarde, David Safford, Serge Hallyn,
Mimi Zohar, Pavel Machek, Greg KH, Christoph Hellwig, Alan Cox,
Rajiv Andrade
Based on Christoph Hellwig's TPM internal kernel interface
locking question, the following TPM changes were made:
- removal of the BKL calls from the TPM driver, which were
added in the overall misc-char-dev-BKL-pushdown.patch
- continue to protect the tpm_chip_list using the
driver_lock, and add an rcu to protect readers.
The TPM internal kernel interface patch will be posted as
part of the integrity patchset.
drivers/char/tpm/tpm.c | 285 +++++++++++++++++++++++++++++++-----------------
drivers/char/tpm/tpm.h | 2 +-
2 files changed, 188 insertions(+), 99 deletions(-)
^ permalink raw reply [flat|nested] 7+ messages in thread* [PATCH 1/2] TPM: update char dev BKL pushdown 2008-08-30 3:05 [PATCH 0/2] TPM Rajiv Andrade @ 2008-08-30 3:05 ` Rajiv Andrade 2008-09-02 15:03 ` Serge E. Hallyn 2008-08-30 3:05 ` [PATCH 2/2] TPM: rcu locking Rajiv Andrade 1 sibling, 1 reply; 7+ messages in thread From: Rajiv Andrade @ 2008-08-30 3:05 UTC (permalink / raw) To: linux-kernel Cc: Andrew Morton, James Morris, Paul McKenney, Peter Dolding, Kenneth Goldman, Debora Velarde, David Safford, Serge Hallyn, Mimi Zohar, Pavel Machek, Greg KH, Christoph Hellwig, Alan Cox, Rajiv Andrade This patch removes the BKL calls from the TPM driver, which were added in the overall misc-char-dev-BKL-pushdown.patch, as they are not needed. In addition, renames num_open to is_open, as only one process can open the file at a time. Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com> Signed-off-by: Rajiv Andrade <srajiv@linux.vnet.ibm.com> --- drivers/char/tpm/tpm.c | 35 ++++++++++++++++++----------------- drivers/char/tpm/tpm.h | 2 +- 2 files changed, 19 insertions(+), 18 deletions(-) diff --git a/drivers/char/tpm/tpm.c b/drivers/char/tpm/tpm.c index ae766d8..59b31e1 100644 --- a/drivers/char/tpm/tpm.c +++ b/drivers/char/tpm/tpm.c @@ -954,13 +954,16 @@ EXPORT_SYMBOL_GPL(tpm_store_cancel); /* * Device file system interface to the TPM + * + * It's assured that the chip will be opened just once, + * by the check of is_open variable, which is protected + * by driver_lock. */ int tpm_open(struct inode *inode, struct file *file) { int rc = 0, minor = iminor(inode); struct tpm_chip *chip = NULL, *pos; - lock_kernel(); spin_lock(&driver_lock); list_for_each_entry(pos, &tpm_chip_list, list) { @@ -975,34 +978,31 @@ int tpm_open(struct inode *inode, struct file *file) goto err_out; } - if (chip->num_opens) { + if (chip->is_open) { dev_dbg(chip->dev, "Another process owns this TPM\n"); rc = -EBUSY; goto err_out; } - chip->num_opens++; - get_device(chip->dev); + chip->is_open = 1; + get_device(chip->dev); /* protect from chip disappearing */ spin_unlock(&driver_lock); chip->data_buffer = kmalloc(TPM_BUFSIZE * sizeof(u8), GFP_KERNEL); if (chip->data_buffer == NULL) { - chip->num_opens--; + chip->is_open = 0; put_device(chip->dev); - unlock_kernel(); return -ENOMEM; } atomic_set(&chip->data_pending, 0); file->private_data = chip; - unlock_kernel(); return 0; err_out: spin_unlock(&driver_lock); - unlock_kernel(); return rc; } EXPORT_SYMBOL_GPL(tpm_open); @@ -1016,7 +1016,7 @@ int tpm_release(struct inode *inode, struct file *file) file->private_data = NULL; del_singleshot_timer_sync(&chip->user_read_timer); atomic_set(&chip->data_pending, 0); - chip->num_opens--; + chip->is_open = 0; put_device(chip->dev); kfree(chip->data_buffer); spin_unlock(&driver_lock); @@ -1082,7 +1082,12 @@ ssize_t tpm_read(struct file *file, char __user *buf, return ret_size; } EXPORT_SYMBOL_GPL(tpm_read); - +/* + * Called on unloading the driver. + * + * First part unloading the chip is done here. The remainder + * is done, when the device count reaches 0, in tpm_dev_release(). + */ void tpm_remove_hardware(struct device *dev) { struct tpm_chip *chip = dev_get_drvdata(dev); @@ -1231,20 +1236,16 @@ struct tpm_chip *tpm_register_hardware(struct device *dev, const struct tpm_vend return NULL; } - spin_lock(&driver_lock); - - list_add(&chip->list, &tpm_chip_list); - - spin_unlock(&driver_lock); - if (sysfs_create_group(&dev->kobj, chip->vendor.attr_group)) { - list_del(&chip->list); misc_deregister(&chip->vendor.miscdev); put_device(chip->dev); return NULL; } chip->bios_dir = tpm_bios_log_setup(devname); + spin_lock(&driver_lock); + list_add(&chip->list, &tpm_chip_list); + spin_unlock(&driver_lock); return chip; } diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h index e885148..2756cab 100644 --- a/drivers/char/tpm/tpm.h +++ b/drivers/char/tpm/tpm.h @@ -90,7 +90,7 @@ struct tpm_chip { struct device *dev; /* Device stuff */ int dev_num; /* /dev/tpm# */ - int num_opens; /* only one allowed */ + unsigned long is_open; /* only one allowed */ int time_expired; /* Data passed to and from the tpm via the read/write calls */ -- 1.5.6.3 ^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [PATCH 1/2] TPM: update char dev BKL pushdown 2008-08-30 3:05 ` [PATCH 1/2] TPM: update char dev BKL pushdown Rajiv Andrade @ 2008-09-02 15:03 ` Serge E. Hallyn 0 siblings, 0 replies; 7+ messages in thread From: Serge E. Hallyn @ 2008-09-02 15:03 UTC (permalink / raw) To: Rajiv Andrade Cc: linux-kernel, Andrew Morton, James Morris, Paul McKenney, Peter Dolding, Kenneth Goldman, Debora Velarde, David Safford, Serge Hallyn, Mimi Zohar, Pavel Machek, Greg KH, Christoph Hellwig, Alan Cox Quoting Rajiv Andrade (srajiv@linux.vnet.ibm.com): > This patch removes the BKL calls from the TPM driver, which > were added in the overall misc-char-dev-BKL-pushdown.patch, > as they are not needed. In addition, renames num_open to > is_open, as only one process can open the file at a time. > > Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com> > Signed-off-by: Rajiv Andrade <srajiv@linux.vnet.ibm.com> Acked-by: Serge Hallyn <serue@us.ibm.com> > --- > drivers/char/tpm/tpm.c | 35 ++++++++++++++++++----------------- > drivers/char/tpm/tpm.h | 2 +- > 2 files changed, 19 insertions(+), 18 deletions(-) > > diff --git a/drivers/char/tpm/tpm.c b/drivers/char/tpm/tpm.c > index ae766d8..59b31e1 100644 > --- a/drivers/char/tpm/tpm.c > +++ b/drivers/char/tpm/tpm.c > @@ -954,13 +954,16 @@ EXPORT_SYMBOL_GPL(tpm_store_cancel); > > /* > * Device file system interface to the TPM > + * > + * It's assured that the chip will be opened just once, > + * by the check of is_open variable, which is protected > + * by driver_lock. > */ > int tpm_open(struct inode *inode, struct file *file) > { > int rc = 0, minor = iminor(inode); > struct tpm_chip *chip = NULL, *pos; > > - lock_kernel(); > spin_lock(&driver_lock); > > list_for_each_entry(pos, &tpm_chip_list, list) { > @@ -975,34 +978,31 @@ int tpm_open(struct inode *inode, struct file *file) > goto err_out; > } > > - if (chip->num_opens) { > + if (chip->is_open) { > dev_dbg(chip->dev, "Another process owns this TPM\n"); > rc = -EBUSY; > goto err_out; > } > > - chip->num_opens++; > - get_device(chip->dev); > + chip->is_open = 1; > + get_device(chip->dev); /* protect from chip disappearing */ > > spin_unlock(&driver_lock); > > chip->data_buffer = kmalloc(TPM_BUFSIZE * sizeof(u8), GFP_KERNEL); > if (chip->data_buffer == NULL) { > - chip->num_opens--; > + chip->is_open = 0; > put_device(chip->dev); > - unlock_kernel(); > return -ENOMEM; > } > > atomic_set(&chip->data_pending, 0); > > file->private_data = chip; > - unlock_kernel(); > return 0; > > err_out: > spin_unlock(&driver_lock); > - unlock_kernel(); > return rc; > } > EXPORT_SYMBOL_GPL(tpm_open); > @@ -1016,7 +1016,7 @@ int tpm_release(struct inode *inode, struct file *file) > file->private_data = NULL; > del_singleshot_timer_sync(&chip->user_read_timer); > atomic_set(&chip->data_pending, 0); > - chip->num_opens--; > + chip->is_open = 0; > put_device(chip->dev); > kfree(chip->data_buffer); > spin_unlock(&driver_lock); > @@ -1082,7 +1082,12 @@ ssize_t tpm_read(struct file *file, char __user *buf, > return ret_size; > } > EXPORT_SYMBOL_GPL(tpm_read); > - > +/* > + * Called on unloading the driver. > + * > + * First part unloading the chip is done here. The remainder > + * is done, when the device count reaches 0, in tpm_dev_release(). > + */ > void tpm_remove_hardware(struct device *dev) > { > struct tpm_chip *chip = dev_get_drvdata(dev); > @@ -1231,20 +1236,16 @@ struct tpm_chip *tpm_register_hardware(struct device *dev, const struct tpm_vend > return NULL; > } > > - spin_lock(&driver_lock); > - > - list_add(&chip->list, &tpm_chip_list); > - > - spin_unlock(&driver_lock); > - > if (sysfs_create_group(&dev->kobj, chip->vendor.attr_group)) { > - list_del(&chip->list); > misc_deregister(&chip->vendor.miscdev); > put_device(chip->dev); > return NULL; > } > > chip->bios_dir = tpm_bios_log_setup(devname); > + spin_lock(&driver_lock); > + list_add(&chip->list, &tpm_chip_list); > + spin_unlock(&driver_lock); > > return chip; > } > diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h > index e885148..2756cab 100644 > --- a/drivers/char/tpm/tpm.h > +++ b/drivers/char/tpm/tpm.h > @@ -90,7 +90,7 @@ struct tpm_chip { > struct device *dev; /* Device stuff */ > > int dev_num; /* /dev/tpm# */ > - int num_opens; /* only one allowed */ > + unsigned long is_open; /* only one allowed */ > int time_expired; > > /* Data passed to and from the tpm via the read/write calls */ > -- > 1.5.6.3 ^ permalink raw reply [flat|nested] 7+ messages in thread
* [PATCH 2/2] TPM: rcu locking 2008-08-30 3:05 [PATCH 0/2] TPM Rajiv Andrade 2008-08-30 3:05 ` [PATCH 1/2] TPM: update char dev BKL pushdown Rajiv Andrade @ 2008-08-30 3:05 ` Rajiv Andrade 2008-08-31 20:28 ` Paul E. McKenney 1 sibling, 1 reply; 7+ messages in thread From: Rajiv Andrade @ 2008-08-30 3:05 UTC (permalink / raw) To: linux-kernel Cc: Andrew Morton, James Morris, Paul McKenney, Peter Dolding, Kenneth Goldman, Debora Velarde, David Safford, Serge Hallyn, Mimi Zohar, Pavel Machek, Greg KH, Christoph Hellwig, Alan Cox, Rajiv Andrade Continue to protect the tpm_chip_list using the driver_lock as before, and add an rcu to protect readers. Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com> Acked-by: Rajiv Andrade <srajiv@linux.vnet.ibm.com> --- drivers/char/tpm/tpm.c | 268 ++++++++++++++++++++++++++++++++---------------- 1 files changed, 178 insertions(+), 90 deletions(-) diff --git a/drivers/char/tpm/tpm.c b/drivers/char/tpm/tpm.c index 59b31e1..704ab01 100644 --- a/drivers/char/tpm/tpm.c +++ b/drivers/char/tpm/tpm.c @@ -587,14 +587,22 @@ ssize_t tpm_show_enabled(struct device * dev, struct device_attribute * attr, { u8 *data; ssize_t rc; + struct tpm_chip *chip; + + rcu_read_lock(); + chip = dev_get_drvdata(dev); + if (chip) + get_device(chip->dev); /* protect from disappearing */ + rcu_read_unlock(); - struct tpm_chip *chip = dev_get_drvdata(dev); if (chip == NULL) return -ENODEV; data = kzalloc(TPM_INTERNAL_RESULT_SIZE, GFP_KERNEL); - if (!data) - return -ENOMEM; + if (!data) { + rc = -ENOMEM; + goto out_alloc; + } memcpy(data, tpm_cap, sizeof(tpm_cap)); data[TPM_CAP_IDX] = TPM_CAP_FLAG; @@ -603,13 +611,15 @@ ssize_t tpm_show_enabled(struct device * dev, struct device_attribute * attr, rc = transmit_cmd(chip, data, TPM_INTERNAL_RESULT_SIZE, "attemtping to determine the permanent enabled state"); if (rc) { - kfree(data); - return 0; + rc = 0; + goto out; } rc = sprintf(buf, "%d\n", !data[TPM_GET_CAP_PERM_DISABLE_IDX]); - +out: kfree(data); +out_alloc: + put_device(chip->dev); return rc; } EXPORT_SYMBOL_GPL(tpm_show_enabled); @@ -619,14 +629,24 @@ ssize_t tpm_show_active(struct device * dev, struct device_attribute * attr, { u8 *data; ssize_t rc; + struct tpm_chip *chip; - struct tpm_chip *chip = dev_get_drvdata(dev); - if (chip == NULL) - return -ENODEV; + rcu_read_lock(); + chip = dev_get_drvdata(dev); + if (chip) + get_device(chip->dev); /* protect from disappearing */ + rcu_read_unlock(); + + if (chip == NULL) { + rc = -ENODEV; + goto out_alloc; + } data = kzalloc(TPM_INTERNAL_RESULT_SIZE, GFP_KERNEL); - if (!data) - return -ENOMEM; + if (!data) { + rc = -ENOMEM; + goto out; + } memcpy(data, tpm_cap, sizeof(tpm_cap)); data[TPM_CAP_IDX] = TPM_CAP_FLAG; @@ -635,13 +655,15 @@ ssize_t tpm_show_active(struct device * dev, struct device_attribute * attr, rc = transmit_cmd(chip, data, TPM_INTERNAL_RESULT_SIZE, "attemtping to determine the permanent active state"); if (rc) { - kfree(data); - return 0; + rc = 0; + goto out; } rc = sprintf(buf, "%d\n", !data[TPM_GET_CAP_PERM_INACTIVE_IDX]); - +out: kfree(data); +out_alloc: + put_device(chip->dev); return rc; } EXPORT_SYMBOL_GPL(tpm_show_active); @@ -651,14 +673,22 @@ ssize_t tpm_show_owned(struct device * dev, struct device_attribute * attr, { u8 *data; ssize_t rc; + struct tpm_chip *chip; + + rcu_read_lock(); + chip = dev_get_drvdata(dev); + if (chip) + get_device(chip->dev); /* protect from disappearing */ + rcu_read_unlock(); - struct tpm_chip *chip = dev_get_drvdata(dev); if (chip == NULL) return -ENODEV; data = kzalloc(TPM_INTERNAL_RESULT_SIZE, GFP_KERNEL); - if (!data) - return -ENOMEM; + if (!data) { + rc = -ENOMEM; + goto out_alloc; + } memcpy(data, tpm_cap, sizeof(tpm_cap)); data[TPM_CAP_IDX] = TPM_CAP_PROP; @@ -667,13 +697,15 @@ ssize_t tpm_show_owned(struct device * dev, struct device_attribute * attr, rc = transmit_cmd(chip, data, TPM_INTERNAL_RESULT_SIZE, "attempting to determine the owner state"); if (rc) { - kfree(data); - return 0; + rc = 0; + goto out; } rc = sprintf(buf, "%d\n", data[TPM_GET_CAP_RET_BOOL_1_IDX]); - +out: kfree(data); +out_alloc: + put_device(chip->dev); return rc; } EXPORT_SYMBOL_GPL(tpm_show_owned); @@ -683,14 +715,22 @@ ssize_t tpm_show_temp_deactivated(struct device * dev, { u8 *data; ssize_t rc; + struct tpm_chip *chip; + + rcu_read_lock(); + chip = dev_get_drvdata(dev); + if (chip) + get_device(chip->dev); /* protect from disappearing */ + rcu_read_unlock(); - struct tpm_chip *chip = dev_get_drvdata(dev); if (chip == NULL) return -ENODEV; data = kzalloc(TPM_INTERNAL_RESULT_SIZE, GFP_KERNEL); - if (!data) - return -ENOMEM; + if (!data) { + rc = -ENOMEM; + goto out_alloc; + } memcpy(data, tpm_cap, sizeof(tpm_cap)); data[TPM_CAP_IDX] = TPM_CAP_FLAG; @@ -699,13 +739,15 @@ ssize_t tpm_show_temp_deactivated(struct device * dev, rc = transmit_cmd(chip, data, TPM_INTERNAL_RESULT_SIZE, "attempting to determine the temporary state"); if (rc) { - kfree(data); - return 0; + rc = 0; + goto out; } rc = sprintf(buf, "%d\n", data[TPM_GET_CAP_TEMP_INACTIVE_IDX]); - +out: kfree(data); +out_alloc: + put_device(chip->dev); return rc; } EXPORT_SYMBOL_GPL(tpm_show_temp_deactivated); @@ -725,14 +767,22 @@ ssize_t tpm_show_pcrs(struct device *dev, struct device_attribute *attr, int i, j, num_pcrs; __be32 index; char *str = buf; + struct tpm_chip *chip; + + rcu_read_lock(); + chip = dev_get_drvdata(dev); + if (chip) + get_device(chip->dev); /* protect from disappearing */ + rcu_read_unlock(); - struct tpm_chip *chip = dev_get_drvdata(dev); if (chip == NULL) return -ENODEV; data = kzalloc(TPM_INTERNAL_RESULT_SIZE, GFP_KERNEL); - if (!data) - return -ENOMEM; + if (!data) { + rc = -ENOMEM; + goto out_alloc; + } memcpy(data, tpm_cap, sizeof(tpm_cap)); data[TPM_CAP_IDX] = TPM_CAP_PROP; @@ -741,8 +791,8 @@ ssize_t tpm_show_pcrs(struct device *dev, struct device_attribute *attr, rc = transmit_cmd(chip, data, TPM_INTERNAL_RESULT_SIZE, "attempting to determine the number of PCRS"); if (rc) { - kfree(data); - return 0; + rc = 0; + goto out; } num_pcrs = be32_to_cpu(*((__be32 *) (data + 14))); @@ -753,15 +803,18 @@ ssize_t tpm_show_pcrs(struct device *dev, struct device_attribute *attr, rc = transmit_cmd(chip, data, TPM_INTERNAL_RESULT_SIZE, "attempting to read a PCR"); if (rc) - goto out; + break; str += sprintf(str, "PCR-%02d: ", i); for (j = 0; j < TPM_DIGEST_SIZE; j++) str += sprintf(str, "%02X ", *(data + 10 + j)); str += sprintf(str, "\n"); } + rc = str - buf; out: kfree(data); - return str - buf; +out_alloc: + put_device(chip->dev); + return rc; } EXPORT_SYMBOL_GPL(tpm_show_pcrs); @@ -779,21 +832,31 @@ ssize_t tpm_show_pubek(struct device *dev, struct device_attribute *attr, ssize_t err; int i, rc; char *str = buf; + struct tpm_chip *chip; + + rcu_read_lock(); + chip = dev_get_drvdata(dev); + if (chip) + get_device(chip->dev); /* protect from disappearing */ + rcu_read_unlock(); - struct tpm_chip *chip = dev_get_drvdata(dev); if (chip == NULL) return -ENODEV; data = kzalloc(READ_PUBEK_RESULT_SIZE, GFP_KERNEL); - if (!data) - return -ENOMEM; + if (!data) { + rc = -ENOMEM; + goto out_alloc; + } memcpy(data, readpubek, sizeof(readpubek)); err = transmit_cmd(chip, data, READ_PUBEK_RESULT_SIZE, "attempting to read the PUBEK"); - if (err) + if (err) { + rc = str - buf; goto out; + } /* ignore header 10 bytes @@ -823,9 +886,11 @@ ssize_t tpm_show_pubek(struct device *dev, struct device_attribute *attr, if ((i + 1) % 16 == 0) str += sprintf(str, "\n"); } -out: rc = str - buf; +out: kfree(data); +out_alloc: + put_device(chip->dev); return rc; } EXPORT_SYMBOL_GPL(tpm_show_pubek); @@ -847,14 +912,22 @@ ssize_t tpm_show_caps(struct device *dev, struct device_attribute *attr, u8 *data; ssize_t rc; char *str = buf; + struct tpm_chip *chip; + + rcu_read_lock(); + chip = dev_get_drvdata(dev); + if (chip) + get_device(chip->dev); /* protect from disappearing */ + rcu_read_unlock(); - struct tpm_chip *chip = dev_get_drvdata(dev); if (chip == NULL) return -ENODEV; data = kzalloc(TPM_INTERNAL_RESULT_SIZE, GFP_KERNEL); - if (!data) - return -ENOMEM; + if (!data) { + rc = -ENOMEM; + goto out_alloc; + } memcpy(data, tpm_cap, sizeof(tpm_cap)); data[TPM_CAP_IDX] = TPM_CAP_PROP; @@ -863,8 +936,8 @@ ssize_t tpm_show_caps(struct device *dev, struct device_attribute *attr, rc = transmit_cmd(chip, data, TPM_INTERNAL_RESULT_SIZE, "attempting to determine the manufacturer"); if (rc) { - kfree(data); - return 0; + rc = 0; + goto out; } str += sprintf(str, "Manufacturer: 0x%x\n", @@ -874,17 +947,22 @@ ssize_t tpm_show_caps(struct device *dev, struct device_attribute *attr, data[CAP_VERSION_IDX] = CAP_VERSION_1_1; rc = transmit_cmd(chip, data, TPM_INTERNAL_RESULT_SIZE, "attempting to determine the 1.1 version"); - if (rc) + if (rc) { + rc = str - buf; goto out; + } str += sprintf(str, "TCG version: %d.%d\nFirmware version: %d.%d\n", (int) data[14], (int) data[15], (int) data[16], (int) data[17]); + rc = str - buf; out: kfree(data); - return str - buf; +out_alloc: + put_device(chip->dev); + return rc; } EXPORT_SYMBOL_GPL(tpm_show_caps); @@ -892,16 +970,25 @@ ssize_t tpm_show_caps_1_2(struct device * dev, struct device_attribute * attr, char *buf) { u8 *data; + ssize_t rc; ssize_t len; char *str = buf; + struct tpm_chip *chip; + + rcu_read_lock(); + chip = dev_get_drvdata(dev); + if (chip) + get_device(chip->dev); /* protect from disappearing */ + rcu_read_unlock(); - struct tpm_chip *chip = dev_get_drvdata(dev); if (chip == NULL) return -ENODEV; data = kzalloc(TPM_INTERNAL_RESULT_SIZE, GFP_KERNEL); - if (!data) - return -ENOMEM; + if (!data) { + rc = -ENOMEM; + goto out_alloc; + } memcpy(data, tpm_cap, sizeof(tpm_cap)); data[TPM_CAP_IDX] = TPM_CAP_PROP; @@ -913,7 +1000,8 @@ ssize_t tpm_show_caps_1_2(struct device * dev, "attempting to determine the manufacturer\n", be32_to_cpu(*((__be32 *) (data + TPM_RET_CODE_IDX)))); kfree(data); - return 0; + rc = 0; + goto out; } str += sprintf(str, "Manufacturer: 0x%x\n", @@ -927,6 +1015,7 @@ ssize_t tpm_show_caps_1_2(struct device * dev, dev_err(chip->dev, "A TPM error (%d) occurred " "attempting to determine the 1.2 version\n", be32_to_cpu(*((__be32 *) (data + TPM_RET_CODE_IDX)))); + rc = str - buf; goto out; } str += sprintf(str, @@ -934,20 +1023,29 @@ ssize_t tpm_show_caps_1_2(struct device * dev, (int) data[16], (int) data[17], (int) data[18], (int) data[19]); + rc = str - buf; out: kfree(data); - return str - buf; +out_alloc: + put_device(chip->dev); + return rc; } EXPORT_SYMBOL_GPL(tpm_show_caps_1_2); ssize_t tpm_store_cancel(struct device *dev, struct device_attribute *attr, const char *buf, size_t count) { - struct tpm_chip *chip = dev_get_drvdata(dev); + struct tpm_chip *chip; + + rcu_read_lock(); + chip = dev_get_drvdata(dev); + if (chip) + get_device(chip->dev); /* protect from disappearing */ + rcu_read_unlock(); if (chip == NULL) return 0; - chip->vendor.cancel(chip); + put_device(chip->dev); return count; } EXPORT_SYMBOL_GPL(tpm_store_cancel); @@ -956,70 +1054,59 @@ EXPORT_SYMBOL_GPL(tpm_store_cancel); * Device file system interface to the TPM * * It's assured that the chip will be opened just once, - * by the check of is_open variable, which is protected - * by driver_lock. + * by the check of is_open variable. */ int tpm_open(struct inode *inode, struct file *file) { - int rc = 0, minor = iminor(inode); + int minor = iminor(inode); struct tpm_chip *chip = NULL, *pos; - spin_lock(&driver_lock); - - list_for_each_entry(pos, &tpm_chip_list, list) { + rcu_read_lock(); + list_for_each_entry_rcu(pos, &tpm_chip_list, list) { if (pos->vendor.miscdev.minor == minor) { chip = pos; + get_device(chip->dev); /* protect from disappearing */ break; } } + rcu_read_unlock(); + if (!chip) + return -ENODEV; - if (chip == NULL) { - rc = -ENODEV; - goto err_out; - } - - if (chip->is_open) { + if (!test_and_set_bit(0, &chip->is_open)) { dev_dbg(chip->dev, "Another process owns this TPM\n"); - rc = -EBUSY; - goto err_out; + return -EBUSY; } - chip->is_open = 1; - get_device(chip->dev); /* protect from chip disappearing */ - - spin_unlock(&driver_lock); - chip->data_buffer = kmalloc(TPM_BUFSIZE * sizeof(u8), GFP_KERNEL); if (chip->data_buffer == NULL) { - chip->is_open = 0; + clear_bit(0, &chip->is_open); put_device(chip->dev); return -ENOMEM; } atomic_set(&chip->data_pending, 0); - file->private_data = chip; return 0; - -err_out: - spin_unlock(&driver_lock); - return rc; } EXPORT_SYMBOL_GPL(tpm_open); +/* + * Called on file close + */ int tpm_release(struct inode *inode, struct file *file) { struct tpm_chip *chip = file->private_data; flush_scheduled_work(); - spin_lock(&driver_lock); file->private_data = NULL; del_singleshot_timer_sync(&chip->user_read_timer); atomic_set(&chip->data_pending, 0); - chip->is_open = 0; - put_device(chip->dev); kfree(chip->data_buffer); - spin_unlock(&driver_lock); + + clear_bit(0, &chip->is_open); + + put_device(chip->dev); return 0; } EXPORT_SYMBOL_GPL(tpm_release); @@ -1082,6 +1169,7 @@ ssize_t tpm_read(struct file *file, char __user *buf, return ret_size; } EXPORT_SYMBOL_GPL(tpm_read); + /* * Called on unloading the driver. * @@ -1098,13 +1186,11 @@ void tpm_remove_hardware(struct device *dev) } spin_lock(&driver_lock); - - list_del(&chip->list); - + list_del_rcu(&chip->list); spin_unlock(&driver_lock); + synchronize_rcu(); misc_deregister(&chip->vendor.miscdev); - sysfs_remove_group(&dev->kobj, chip->vendor.attr_group); tpm_bios_log_teardown(chip->bios_dir); @@ -1152,8 +1238,7 @@ EXPORT_SYMBOL_GPL(tpm_pm_resume); /* * Once all references to platform device are down to 0, * release all allocated structures. - * In case vendor provided release function, - * call it too. + * In case vendor provided release function, call it too. */ static void tpm_dev_release(struct device *dev) { @@ -1176,8 +1261,8 @@ static void tpm_dev_release(struct device *dev) * upon errant exit from this function specific probe function should call * pci_disable_device */ -struct tpm_chip *tpm_register_hardware(struct device *dev, const struct tpm_vendor_specific - *entry) +struct tpm_chip *tpm_register_hardware(struct device *dev, + const struct tpm_vendor_specific *entry) { #define DEVNAME_SIZE 7 @@ -1243,9 +1328,12 @@ struct tpm_chip *tpm_register_hardware(struct device *dev, const struct tpm_vend } chip->bios_dir = tpm_bios_log_setup(devname); + + /* Make chip available */ spin_lock(&driver_lock); - list_add(&chip->list, &tpm_chip_list); + list_add_rcu(&chip->list, &tpm_chip_list); spin_unlock(&driver_lock); + synchronize_rcu(); return chip; } -- 1.5.6.3 ^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [PATCH 2/2] TPM: rcu locking 2008-08-30 3:05 ` [PATCH 2/2] TPM: rcu locking Rajiv Andrade @ 2008-08-31 20:28 ` Paul E. McKenney 2008-09-02 15:19 ` Serge E. Hallyn 2008-09-11 18:16 ` Mimi Zohar 0 siblings, 2 replies; 7+ messages in thread From: Paul E. McKenney @ 2008-08-31 20:28 UTC (permalink / raw) To: Rajiv Andrade Cc: linux-kernel, Andrew Morton, James Morris, Peter Dolding, Kenneth Goldman, Debora Velarde, David Safford, Serge Hallyn, Mimi Zohar, Pavel Machek, Greg KH, Christoph Hellwig, Alan Cox On Sat, Aug 30, 2008 at 12:05:04AM -0300, Rajiv Andrade wrote: > Continue to protect the tpm_chip_list using the driver_lock > as before, and add an rcu to protect readers. A few questions interspersed below... Thanx, Paul > Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com> > Acked-by: Rajiv Andrade <srajiv@linux.vnet.ibm.com> > --- > drivers/char/tpm/tpm.c | 268 ++++++++++++++++++++++++++++++++---------------- > 1 files changed, 178 insertions(+), 90 deletions(-) > > diff --git a/drivers/char/tpm/tpm.c b/drivers/char/tpm/tpm.c > index 59b31e1..704ab01 100644 > --- a/drivers/char/tpm/tpm.c > +++ b/drivers/char/tpm/tpm.c > @@ -587,14 +587,22 @@ ssize_t tpm_show_enabled(struct device * dev, struct device_attribute * attr, > { > u8 *data; > ssize_t rc; > + struct tpm_chip *chip; > + The following five lines of code appear repeatedly. Why not put them into an inline function or a macro? Also, doesn't there need to be an rcu_dereference() somewhere either in this sequence of code or in either dev_get_drvdata() or get_device()? Or am I missing something subtle here? >From what I see of the code, I actually don't understand why the rcu_read_lock() is needed here -- only tpm_chip_list is covered by the RCU list addition/deletion primitives in this patch. If you are adding a multilinked data structure into an RCU-protected list, you need RCU traversal primitives only when traversing the list, not the data structure contained in the list. (Of course, any changes to the data structure contained in the list must be protected somehow or other, unless there are no such changes.) > + rcu_read_lock(); > + chip = dev_get_drvdata(dev); > + if (chip) > + get_device(chip->dev); /* protect from disappearing */ > + rcu_read_unlock(); > > - struct tpm_chip *chip = dev_get_drvdata(dev); > if (chip == NULL) > return -ENODEV; > > data = kzalloc(TPM_INTERNAL_RESULT_SIZE, GFP_KERNEL); > - if (!data) > - return -ENOMEM; > + if (!data) { > + rc = -ENOMEM; > + goto out_alloc; > + } > > memcpy(data, tpm_cap, sizeof(tpm_cap)); > data[TPM_CAP_IDX] = TPM_CAP_FLAG; > @@ -603,13 +611,15 @@ ssize_t tpm_show_enabled(struct device * dev, struct device_attribute * attr, > rc = transmit_cmd(chip, data, TPM_INTERNAL_RESULT_SIZE, > "attemtping to determine the permanent enabled state"); > if (rc) { > - kfree(data); > - return 0; > + rc = 0; > + goto out; > } > > rc = sprintf(buf, "%d\n", !data[TPM_GET_CAP_PERM_DISABLE_IDX]); > - > +out: > kfree(data); > +out_alloc: > + put_device(chip->dev); > return rc; > } > EXPORT_SYMBOL_GPL(tpm_show_enabled); > @@ -619,14 +629,24 @@ ssize_t tpm_show_active(struct device * dev, struct device_attribute * attr, > { > u8 *data; > ssize_t rc; > + struct tpm_chip *chip; > > - struct tpm_chip *chip = dev_get_drvdata(dev); > - if (chip == NULL) > - return -ENODEV; > + rcu_read_lock(); > + chip = dev_get_drvdata(dev); > + if (chip) > + get_device(chip->dev); /* protect from disappearing */ > + rcu_read_unlock(); > + > + if (chip == NULL) { > + rc = -ENODEV; > + goto out_alloc; > + } > > data = kzalloc(TPM_INTERNAL_RESULT_SIZE, GFP_KERNEL); > - if (!data) > - return -ENOMEM; > + if (!data) { > + rc = -ENOMEM; > + goto out; > + } > > memcpy(data, tpm_cap, sizeof(tpm_cap)); > data[TPM_CAP_IDX] = TPM_CAP_FLAG; > @@ -635,13 +655,15 @@ ssize_t tpm_show_active(struct device * dev, struct device_attribute * attr, > rc = transmit_cmd(chip, data, TPM_INTERNAL_RESULT_SIZE, > "attemtping to determine the permanent active state"); > if (rc) { > - kfree(data); > - return 0; > + rc = 0; > + goto out; > } > > rc = sprintf(buf, "%d\n", !data[TPM_GET_CAP_PERM_INACTIVE_IDX]); > - > +out: > kfree(data); > +out_alloc: > + put_device(chip->dev); > return rc; > } > EXPORT_SYMBOL_GPL(tpm_show_active); > @@ -651,14 +673,22 @@ ssize_t tpm_show_owned(struct device * dev, struct device_attribute * attr, > { > u8 *data; > ssize_t rc; > + struct tpm_chip *chip; > + > + rcu_read_lock(); > + chip = dev_get_drvdata(dev); > + if (chip) > + get_device(chip->dev); /* protect from disappearing */ > + rcu_read_unlock(); > > - struct tpm_chip *chip = dev_get_drvdata(dev); > if (chip == NULL) > return -ENODEV; > > data = kzalloc(TPM_INTERNAL_RESULT_SIZE, GFP_KERNEL); > - if (!data) > - return -ENOMEM; > + if (!data) { > + rc = -ENOMEM; > + goto out_alloc; > + } > > memcpy(data, tpm_cap, sizeof(tpm_cap)); > data[TPM_CAP_IDX] = TPM_CAP_PROP; > @@ -667,13 +697,15 @@ ssize_t tpm_show_owned(struct device * dev, struct device_attribute * attr, > rc = transmit_cmd(chip, data, TPM_INTERNAL_RESULT_SIZE, > "attempting to determine the owner state"); > if (rc) { > - kfree(data); > - return 0; > + rc = 0; > + goto out; > } > > rc = sprintf(buf, "%d\n", data[TPM_GET_CAP_RET_BOOL_1_IDX]); > - > +out: > kfree(data); > +out_alloc: > + put_device(chip->dev); > return rc; > } > EXPORT_SYMBOL_GPL(tpm_show_owned); > @@ -683,14 +715,22 @@ ssize_t tpm_show_temp_deactivated(struct device * dev, > { > u8 *data; > ssize_t rc; > + struct tpm_chip *chip; > + > + rcu_read_lock(); > + chip = dev_get_drvdata(dev); > + if (chip) > + get_device(chip->dev); /* protect from disappearing */ > + rcu_read_unlock(); > > - struct tpm_chip *chip = dev_get_drvdata(dev); > if (chip == NULL) > return -ENODEV; > > data = kzalloc(TPM_INTERNAL_RESULT_SIZE, GFP_KERNEL); > - if (!data) > - return -ENOMEM; > + if (!data) { > + rc = -ENOMEM; > + goto out_alloc; > + } > > memcpy(data, tpm_cap, sizeof(tpm_cap)); > data[TPM_CAP_IDX] = TPM_CAP_FLAG; > @@ -699,13 +739,15 @@ ssize_t tpm_show_temp_deactivated(struct device * dev, > rc = transmit_cmd(chip, data, TPM_INTERNAL_RESULT_SIZE, > "attempting to determine the temporary state"); > if (rc) { > - kfree(data); > - return 0; > + rc = 0; > + goto out; > } > > rc = sprintf(buf, "%d\n", data[TPM_GET_CAP_TEMP_INACTIVE_IDX]); > - > +out: > kfree(data); > +out_alloc: > + put_device(chip->dev); > return rc; > } > EXPORT_SYMBOL_GPL(tpm_show_temp_deactivated); > @@ -725,14 +767,22 @@ ssize_t tpm_show_pcrs(struct device *dev, struct device_attribute *attr, > int i, j, num_pcrs; > __be32 index; > char *str = buf; > + struct tpm_chip *chip; > + > + rcu_read_lock(); > + chip = dev_get_drvdata(dev); > + if (chip) > + get_device(chip->dev); /* protect from disappearing */ > + rcu_read_unlock(); > > - struct tpm_chip *chip = dev_get_drvdata(dev); > if (chip == NULL) > return -ENODEV; > > data = kzalloc(TPM_INTERNAL_RESULT_SIZE, GFP_KERNEL); > - if (!data) > - return -ENOMEM; > + if (!data) { > + rc = -ENOMEM; > + goto out_alloc; > + } > > memcpy(data, tpm_cap, sizeof(tpm_cap)); > data[TPM_CAP_IDX] = TPM_CAP_PROP; > @@ -741,8 +791,8 @@ ssize_t tpm_show_pcrs(struct device *dev, struct device_attribute *attr, > rc = transmit_cmd(chip, data, TPM_INTERNAL_RESULT_SIZE, > "attempting to determine the number of PCRS"); > if (rc) { > - kfree(data); > - return 0; > + rc = 0; > + goto out; > } > > num_pcrs = be32_to_cpu(*((__be32 *) (data + 14))); > @@ -753,15 +803,18 @@ ssize_t tpm_show_pcrs(struct device *dev, struct device_attribute *attr, > rc = transmit_cmd(chip, data, TPM_INTERNAL_RESULT_SIZE, > "attempting to read a PCR"); > if (rc) > - goto out; > + break; > str += sprintf(str, "PCR-%02d: ", i); > for (j = 0; j < TPM_DIGEST_SIZE; j++) > str += sprintf(str, "%02X ", *(data + 10 + j)); > str += sprintf(str, "\n"); > } > + rc = str - buf; > out: > kfree(data); > - return str - buf; > +out_alloc: > + put_device(chip->dev); > + return rc; > } > EXPORT_SYMBOL_GPL(tpm_show_pcrs); > > @@ -779,21 +832,31 @@ ssize_t tpm_show_pubek(struct device *dev, struct device_attribute *attr, > ssize_t err; > int i, rc; > char *str = buf; > + struct tpm_chip *chip; > + > + rcu_read_lock(); > + chip = dev_get_drvdata(dev); > + if (chip) > + get_device(chip->dev); /* protect from disappearing */ > + rcu_read_unlock(); > > - struct tpm_chip *chip = dev_get_drvdata(dev); > if (chip == NULL) > return -ENODEV; > > data = kzalloc(READ_PUBEK_RESULT_SIZE, GFP_KERNEL); > - if (!data) > - return -ENOMEM; > + if (!data) { > + rc = -ENOMEM; > + goto out_alloc; > + } > > memcpy(data, readpubek, sizeof(readpubek)); > > err = transmit_cmd(chip, data, READ_PUBEK_RESULT_SIZE, > "attempting to read the PUBEK"); > - if (err) > + if (err) { > + rc = str - buf; > goto out; > + } > > /* > ignore header 10 bytes > @@ -823,9 +886,11 @@ ssize_t tpm_show_pubek(struct device *dev, struct device_attribute *attr, > if ((i + 1) % 16 == 0) > str += sprintf(str, "\n"); > } > -out: > rc = str - buf; > +out: > kfree(data); > +out_alloc: > + put_device(chip->dev); > return rc; > } > EXPORT_SYMBOL_GPL(tpm_show_pubek); > @@ -847,14 +912,22 @@ ssize_t tpm_show_caps(struct device *dev, struct device_attribute *attr, > u8 *data; > ssize_t rc; > char *str = buf; > + struct tpm_chip *chip; > + > + rcu_read_lock(); > + chip = dev_get_drvdata(dev); > + if (chip) > + get_device(chip->dev); /* protect from disappearing */ > + rcu_read_unlock(); > > - struct tpm_chip *chip = dev_get_drvdata(dev); > if (chip == NULL) > return -ENODEV; > > data = kzalloc(TPM_INTERNAL_RESULT_SIZE, GFP_KERNEL); > - if (!data) > - return -ENOMEM; > + if (!data) { > + rc = -ENOMEM; > + goto out_alloc; > + } > > memcpy(data, tpm_cap, sizeof(tpm_cap)); > data[TPM_CAP_IDX] = TPM_CAP_PROP; > @@ -863,8 +936,8 @@ ssize_t tpm_show_caps(struct device *dev, struct device_attribute *attr, > rc = transmit_cmd(chip, data, TPM_INTERNAL_RESULT_SIZE, > "attempting to determine the manufacturer"); > if (rc) { > - kfree(data); > - return 0; > + rc = 0; > + goto out; > } > > str += sprintf(str, "Manufacturer: 0x%x\n", > @@ -874,17 +947,22 @@ ssize_t tpm_show_caps(struct device *dev, struct device_attribute *attr, > data[CAP_VERSION_IDX] = CAP_VERSION_1_1; > rc = transmit_cmd(chip, data, TPM_INTERNAL_RESULT_SIZE, > "attempting to determine the 1.1 version"); > - if (rc) > + if (rc) { > + rc = str - buf; > goto out; > + } > > str += sprintf(str, > "TCG version: %d.%d\nFirmware version: %d.%d\n", > (int) data[14], (int) data[15], (int) data[16], > (int) data[17]); > > + rc = str - buf; > out: > kfree(data); > - return str - buf; > +out_alloc: > + put_device(chip->dev); > + return rc; > } > EXPORT_SYMBOL_GPL(tpm_show_caps); > > @@ -892,16 +970,25 @@ ssize_t tpm_show_caps_1_2(struct device * dev, > struct device_attribute * attr, char *buf) > { > u8 *data; > + ssize_t rc; > ssize_t len; > char *str = buf; > + struct tpm_chip *chip; > + > + rcu_read_lock(); > + chip = dev_get_drvdata(dev); > + if (chip) > + get_device(chip->dev); /* protect from disappearing */ > + rcu_read_unlock(); > > - struct tpm_chip *chip = dev_get_drvdata(dev); > if (chip == NULL) > return -ENODEV; > > data = kzalloc(TPM_INTERNAL_RESULT_SIZE, GFP_KERNEL); > - if (!data) > - return -ENOMEM; > + if (!data) { > + rc = -ENOMEM; > + goto out_alloc; > + } > > memcpy(data, tpm_cap, sizeof(tpm_cap)); > data[TPM_CAP_IDX] = TPM_CAP_PROP; > @@ -913,7 +1000,8 @@ ssize_t tpm_show_caps_1_2(struct device * dev, > "attempting to determine the manufacturer\n", > be32_to_cpu(*((__be32 *) (data + TPM_RET_CODE_IDX)))); > kfree(data); > - return 0; > + rc = 0; > + goto out; > } > > str += sprintf(str, "Manufacturer: 0x%x\n", > @@ -927,6 +1015,7 @@ ssize_t tpm_show_caps_1_2(struct device * dev, > dev_err(chip->dev, "A TPM error (%d) occurred " > "attempting to determine the 1.2 version\n", > be32_to_cpu(*((__be32 *) (data + TPM_RET_CODE_IDX)))); > + rc = str - buf; > goto out; > } > str += sprintf(str, > @@ -934,20 +1023,29 @@ ssize_t tpm_show_caps_1_2(struct device * dev, > (int) data[16], (int) data[17], (int) data[18], > (int) data[19]); > > + rc = str - buf; > out: > kfree(data); > - return str - buf; > +out_alloc: > + put_device(chip->dev); > + return rc; > } > EXPORT_SYMBOL_GPL(tpm_show_caps_1_2); > > ssize_t tpm_store_cancel(struct device *dev, struct device_attribute *attr, > const char *buf, size_t count) > { > - struct tpm_chip *chip = dev_get_drvdata(dev); > + struct tpm_chip *chip; > + > + rcu_read_lock(); > + chip = dev_get_drvdata(dev); > + if (chip) > + get_device(chip->dev); /* protect from disappearing */ > + rcu_read_unlock(); > if (chip == NULL) > return 0; > - > chip->vendor.cancel(chip); > + put_device(chip->dev); > return count; > } > EXPORT_SYMBOL_GPL(tpm_store_cancel); > @@ -956,70 +1054,59 @@ EXPORT_SYMBOL_GPL(tpm_store_cancel); > * Device file system interface to the TPM > * > * It's assured that the chip will be opened just once, > - * by the check of is_open variable, which is protected > - * by driver_lock. > + * by the check of is_open variable. > */ > int tpm_open(struct inode *inode, struct file *file) > { > - int rc = 0, minor = iminor(inode); > + int minor = iminor(inode); > struct tpm_chip *chip = NULL, *pos; > > - spin_lock(&driver_lock); > - > - list_for_each_entry(pos, &tpm_chip_list, list) { > + rcu_read_lock(); > + list_for_each_entry_rcu(pos, &tpm_chip_list, list) { > if (pos->vendor.miscdev.minor == minor) { > chip = pos; > + get_device(chip->dev); /* protect from disappearing */ > break; > } > } > + rcu_read_unlock(); > + if (!chip) > + return -ENODEV; > > - if (chip == NULL) { > - rc = -ENODEV; > - goto err_out; > - } > - > - if (chip->is_open) { > + if (!test_and_set_bit(0, &chip->is_open)) { > dev_dbg(chip->dev, "Another process owns this TPM\n"); > - rc = -EBUSY; > - goto err_out; > + return -EBUSY; > } > > - chip->is_open = 1; > - get_device(chip->dev); /* protect from chip disappearing */ > - > - spin_unlock(&driver_lock); > - > chip->data_buffer = kmalloc(TPM_BUFSIZE * sizeof(u8), GFP_KERNEL); > if (chip->data_buffer == NULL) { > - chip->is_open = 0; > + clear_bit(0, &chip->is_open); > put_device(chip->dev); > return -ENOMEM; > } > > atomic_set(&chip->data_pending, 0); > - > file->private_data = chip; > return 0; > - > -err_out: > - spin_unlock(&driver_lock); > - return rc; > } > EXPORT_SYMBOL_GPL(tpm_open); > > +/* > + * Called on file close > + */ > int tpm_release(struct inode *inode, struct file *file) > { > struct tpm_chip *chip = file->private_data; > > flush_scheduled_work(); > - spin_lock(&driver_lock); > file->private_data = NULL; > del_singleshot_timer_sync(&chip->user_read_timer); > atomic_set(&chip->data_pending, 0); > - chip->is_open = 0; > - put_device(chip->dev); > kfree(chip->data_buffer); > - spin_unlock(&driver_lock); > + > + clear_bit(0, &chip->is_open); > + > + put_device(chip->dev); > return 0; > } > EXPORT_SYMBOL_GPL(tpm_release); > @@ -1082,6 +1169,7 @@ ssize_t tpm_read(struct file *file, char __user *buf, > return ret_size; > } > EXPORT_SYMBOL_GPL(tpm_read); > + > /* > * Called on unloading the driver. > * > @@ -1098,13 +1186,11 @@ void tpm_remove_hardware(struct device *dev) > } > > spin_lock(&driver_lock); > - > - list_del(&chip->list); > - > + list_del_rcu(&chip->list); > spin_unlock(&driver_lock); > + synchronize_rcu(); > > misc_deregister(&chip->vendor.miscdev); > - > sysfs_remove_group(&dev->kobj, chip->vendor.attr_group); > tpm_bios_log_teardown(chip->bios_dir); > > @@ -1152,8 +1238,7 @@ EXPORT_SYMBOL_GPL(tpm_pm_resume); > /* > * Once all references to platform device are down to 0, > * release all allocated structures. > - * In case vendor provided release function, > - * call it too. > + * In case vendor provided release function, call it too. > */ > static void tpm_dev_release(struct device *dev) > { > @@ -1176,8 +1261,8 @@ static void tpm_dev_release(struct device *dev) > * upon errant exit from this function specific probe function should call > * pci_disable_device > */ > -struct tpm_chip *tpm_register_hardware(struct device *dev, const struct tpm_vendor_specific > - *entry) > +struct tpm_chip *tpm_register_hardware(struct device *dev, > + const struct tpm_vendor_specific *entry) > { > #define DEVNAME_SIZE 7 > > @@ -1243,9 +1328,12 @@ struct tpm_chip *tpm_register_hardware(struct device *dev, const struct tpm_vend > } > > chip->bios_dir = tpm_bios_log_setup(devname); > + > + /* Make chip available */ > spin_lock(&driver_lock); > - list_add(&chip->list, &tpm_chip_list); > + list_add_rcu(&chip->list, &tpm_chip_list); > spin_unlock(&driver_lock); > + synchronize_rcu(); The above synchronize_rcu() is not needed -- unless it is required that tpm_register_hardware() not return until it can be guaranteed that all subsequent readers will see the new entry. (Of course, the current CPU/task is guaranteed to see it in any subsequent call, even without the synchronize_rcu().) > return chip; > } > -- > 1.5.6.3 > ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH 2/2] TPM: rcu locking 2008-08-31 20:28 ` Paul E. McKenney @ 2008-09-02 15:19 ` Serge E. Hallyn 2008-09-11 18:16 ` Mimi Zohar 1 sibling, 0 replies; 7+ messages in thread From: Serge E. Hallyn @ 2008-09-02 15:19 UTC (permalink / raw) To: Paul E. McKenney Cc: Rajiv Andrade, linux-kernel, Andrew Morton, James Morris, Peter Dolding, Kenneth Goldman, Debora Velarde, David Safford, Serge Hallyn, Mimi Zohar, Pavel Machek, Greg KH, Christoph Hellwig, Alan Cox Quoting Paul E. McKenney (paulmck@linux.vnet.ibm.com): > On Sat, Aug 30, 2008 at 12:05:04AM -0300, Rajiv Andrade wrote: > > Continue to protect the tpm_chip_list using the driver_lock > > as before, and add an rcu to protect readers. > > A few questions interspersed below... > > Thanx, Paul > > > Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com> > > Acked-by: Rajiv Andrade <srajiv@linux.vnet.ibm.com> > > --- > > drivers/char/tpm/tpm.c | 268 ++++++++++++++++++++++++++++++++---------------- > > 1 files changed, 178 insertions(+), 90 deletions(-) > > > > diff --git a/drivers/char/tpm/tpm.c b/drivers/char/tpm/tpm.c > > index 59b31e1..704ab01 100644 > > --- a/drivers/char/tpm/tpm.c > > +++ b/drivers/char/tpm/tpm.c > > @@ -587,14 +587,22 @@ ssize_t tpm_show_enabled(struct device * dev, struct device_attribute * attr, > > { > > u8 *data; > > ssize_t rc; > > + struct tpm_chip *chip; > > + > > The following five lines of code appear repeatedly. Why not put them > into an inline function or a macro? Yes, a good idea, because in the second repetition of this code sequence you have the wrong set of gotos, and can end up doing put_device(chip->dev) when dev is NULL :) > Also, doesn't there need to be an rcu_dereference() somewhere either in > this sequence of code or in either dev_get_drvdata() or get_device()? > Or am I missing something subtle here? > > >From what I see of the code, I actually don't understand why the > rcu_read_lock() is needed here -- only tpm_chip_list is covered by Good point. Which I missed entirely when I saw the patch before. Taking the case of tpm_show_enabled(), it is called as a sysfs file callback, right? So the sysfs/kobject infrastructure will pin the device for the duration of the callback I presume? > the RCU list addition/deletion primitives in this patch. If you are > adding a multilinked data structure into an RCU-protected list, you > need RCU traversal primitives only when traversing the list, not the > data structure contained in the list. (Of course, any changes to the > data structure contained in the list must be protected somehow or other, > unless there are no such changes.) > > > + rcu_read_lock(); > > + chip = dev_get_drvdata(dev); > > + if (chip) > > + get_device(chip->dev); /* protect from disappearing */ > > + rcu_read_unlock(); > > > > - struct tpm_chip *chip = dev_get_drvdata(dev); > > if (chip == NULL) > > return -ENODEV; > > > > data = kzalloc(TPM_INTERNAL_RESULT_SIZE, GFP_KERNEL); > > - if (!data) > > - return -ENOMEM; > > + if (!data) { > > + rc = -ENOMEM; > > + goto out_alloc; > > + } > > > > memcpy(data, tpm_cap, sizeof(tpm_cap)); > > data[TPM_CAP_IDX] = TPM_CAP_FLAG; > > @@ -603,13 +611,15 @@ ssize_t tpm_show_enabled(struct device * dev, struct device_attribute * attr, > > rc = transmit_cmd(chip, data, TPM_INTERNAL_RESULT_SIZE, > > "attemtping to determine the permanent enabled state"); > > if (rc) { > > - kfree(data); > > - return 0; > > + rc = 0; > > + goto out; > > } > > > > rc = sprintf(buf, "%d\n", !data[TPM_GET_CAP_PERM_DISABLE_IDX]); > > - > > +out: > > kfree(data); > > +out_alloc: > > + put_device(chip->dev); > > return rc; > > } > > EXPORT_SYMBOL_GPL(tpm_show_enabled); > > @@ -619,14 +629,24 @@ ssize_t tpm_show_active(struct device * dev, struct device_attribute * attr, > > { > > u8 *data; > > ssize_t rc; > > + struct tpm_chip *chip; > > > > - struct tpm_chip *chip = dev_get_drvdata(dev); > > - if (chip == NULL) > > - return -ENODEV; > > + rcu_read_lock(); > > + chip = dev_get_drvdata(dev); > > + if (chip) > > + get_device(chip->dev); /* protect from disappearing */ > > + rcu_read_unlock(); > > + > > + if (chip == NULL) { > > + rc = -ENODEV; > > + goto out_alloc; > > + } > > > > data = kzalloc(TPM_INTERNAL_RESULT_SIZE, GFP_KERNEL); > > - if (!data) > > - return -ENOMEM; > > + if (!data) { > > + rc = -ENOMEM; > > + goto out; > > + } > > > > memcpy(data, tpm_cap, sizeof(tpm_cap)); > > data[TPM_CAP_IDX] = TPM_CAP_FLAG; > > @@ -635,13 +655,15 @@ ssize_t tpm_show_active(struct device * dev, struct device_attribute * attr, > > rc = transmit_cmd(chip, data, TPM_INTERNAL_RESULT_SIZE, > > "attemtping to determine the permanent active state"); > > if (rc) { > > - kfree(data); > > - return 0; > > + rc = 0; > > + goto out; > > } > > > > rc = sprintf(buf, "%d\n", !data[TPM_GET_CAP_PERM_INACTIVE_IDX]); > > - > > +out: > > kfree(data); > > +out_alloc: > > + put_device(chip->dev); > > return rc; > > } > > EXPORT_SYMBOL_GPL(tpm_show_active); > > @@ -651,14 +673,22 @@ ssize_t tpm_show_owned(struct device * dev, struct device_attribute * attr, > > { > > u8 *data; > > ssize_t rc; > > + struct tpm_chip *chip; > > + > > + rcu_read_lock(); > > + chip = dev_get_drvdata(dev); > > + if (chip) > > + get_device(chip->dev); /* protect from disappearing */ > > + rcu_read_unlock(); > > > > - struct tpm_chip *chip = dev_get_drvdata(dev); > > if (chip == NULL) > > return -ENODEV; > > > > data = kzalloc(TPM_INTERNAL_RESULT_SIZE, GFP_KERNEL); > > - if (!data) > > - return -ENOMEM; > > + if (!data) { > > + rc = -ENOMEM; > > + goto out_alloc; > > + } > > > > memcpy(data, tpm_cap, sizeof(tpm_cap)); > > data[TPM_CAP_IDX] = TPM_CAP_PROP; > > @@ -667,13 +697,15 @@ ssize_t tpm_show_owned(struct device * dev, struct device_attribute * attr, > > rc = transmit_cmd(chip, data, TPM_INTERNAL_RESULT_SIZE, > > "attempting to determine the owner state"); > > if (rc) { > > - kfree(data); > > - return 0; > > + rc = 0; > > + goto out; > > } > > > > rc = sprintf(buf, "%d\n", data[TPM_GET_CAP_RET_BOOL_1_IDX]); > > - > > +out: > > kfree(data); > > +out_alloc: > > + put_device(chip->dev); > > return rc; > > } > > EXPORT_SYMBOL_GPL(tpm_show_owned); > > @@ -683,14 +715,22 @@ ssize_t tpm_show_temp_deactivated(struct device * dev, > > { > > u8 *data; > > ssize_t rc; > > + struct tpm_chip *chip; > > + > > + rcu_read_lock(); > > + chip = dev_get_drvdata(dev); > > + if (chip) > > + get_device(chip->dev); /* protect from disappearing */ > > + rcu_read_unlock(); > > > > - struct tpm_chip *chip = dev_get_drvdata(dev); > > if (chip == NULL) > > return -ENODEV; > > > > data = kzalloc(TPM_INTERNAL_RESULT_SIZE, GFP_KERNEL); > > - if (!data) > > - return -ENOMEM; > > + if (!data) { > > + rc = -ENOMEM; > > + goto out_alloc; > > + } > > > > memcpy(data, tpm_cap, sizeof(tpm_cap)); > > data[TPM_CAP_IDX] = TPM_CAP_FLAG; > > @@ -699,13 +739,15 @@ ssize_t tpm_show_temp_deactivated(struct device * dev, > > rc = transmit_cmd(chip, data, TPM_INTERNAL_RESULT_SIZE, > > "attempting to determine the temporary state"); > > if (rc) { > > - kfree(data); > > - return 0; > > + rc = 0; > > + goto out; > > } > > > > rc = sprintf(buf, "%d\n", data[TPM_GET_CAP_TEMP_INACTIVE_IDX]); > > - > > +out: > > kfree(data); > > +out_alloc: > > + put_device(chip->dev); > > return rc; > > } > > EXPORT_SYMBOL_GPL(tpm_show_temp_deactivated); > > @@ -725,14 +767,22 @@ ssize_t tpm_show_pcrs(struct device *dev, struct device_attribute *attr, > > int i, j, num_pcrs; > > __be32 index; > > char *str = buf; > > + struct tpm_chip *chip; > > + > > + rcu_read_lock(); > > + chip = dev_get_drvdata(dev); > > + if (chip) > > + get_device(chip->dev); /* protect from disappearing */ > > + rcu_read_unlock(); > > > > - struct tpm_chip *chip = dev_get_drvdata(dev); > > if (chip == NULL) > > return -ENODEV; > > > > data = kzalloc(TPM_INTERNAL_RESULT_SIZE, GFP_KERNEL); > > - if (!data) > > - return -ENOMEM; > > + if (!data) { > > + rc = -ENOMEM; > > + goto out_alloc; > > + } > > > > memcpy(data, tpm_cap, sizeof(tpm_cap)); > > data[TPM_CAP_IDX] = TPM_CAP_PROP; > > @@ -741,8 +791,8 @@ ssize_t tpm_show_pcrs(struct device *dev, struct device_attribute *attr, > > rc = transmit_cmd(chip, data, TPM_INTERNAL_RESULT_SIZE, > > "attempting to determine the number of PCRS"); > > if (rc) { > > - kfree(data); > > - return 0; > > + rc = 0; > > + goto out; > > } > > > > num_pcrs = be32_to_cpu(*((__be32 *) (data + 14))); > > @@ -753,15 +803,18 @@ ssize_t tpm_show_pcrs(struct device *dev, struct device_attribute *attr, > > rc = transmit_cmd(chip, data, TPM_INTERNAL_RESULT_SIZE, > > "attempting to read a PCR"); > > if (rc) > > - goto out; > > + break; > > str += sprintf(str, "PCR-%02d: ", i); > > for (j = 0; j < TPM_DIGEST_SIZE; j++) > > str += sprintf(str, "%02X ", *(data + 10 + j)); > > str += sprintf(str, "\n"); > > } > > + rc = str - buf; > > out: > > kfree(data); > > - return str - buf; > > +out_alloc: > > + put_device(chip->dev); > > + return rc; > > } > > EXPORT_SYMBOL_GPL(tpm_show_pcrs); > > > > @@ -779,21 +832,31 @@ ssize_t tpm_show_pubek(struct device *dev, struct device_attribute *attr, > > ssize_t err; > > int i, rc; > > char *str = buf; > > + struct tpm_chip *chip; > > + > > + rcu_read_lock(); > > + chip = dev_get_drvdata(dev); > > + if (chip) > > + get_device(chip->dev); /* protect from disappearing */ > > + rcu_read_unlock(); > > > > - struct tpm_chip *chip = dev_get_drvdata(dev); > > if (chip == NULL) > > return -ENODEV; > > > > data = kzalloc(READ_PUBEK_RESULT_SIZE, GFP_KERNEL); > > - if (!data) > > - return -ENOMEM; > > + if (!data) { > > + rc = -ENOMEM; > > + goto out_alloc; > > + } > > > > memcpy(data, readpubek, sizeof(readpubek)); > > > > err = transmit_cmd(chip, data, READ_PUBEK_RESULT_SIZE, > > "attempting to read the PUBEK"); > > - if (err) > > + if (err) { > > + rc = str - buf; > > goto out; > > + } > > > > /* > > ignore header 10 bytes > > @@ -823,9 +886,11 @@ ssize_t tpm_show_pubek(struct device *dev, struct device_attribute *attr, > > if ((i + 1) % 16 == 0) > > str += sprintf(str, "\n"); > > } > > -out: > > rc = str - buf; > > +out: > > kfree(data); > > +out_alloc: > > + put_device(chip->dev); > > return rc; > > } > > EXPORT_SYMBOL_GPL(tpm_show_pubek); > > @@ -847,14 +912,22 @@ ssize_t tpm_show_caps(struct device *dev, struct device_attribute *attr, > > u8 *data; > > ssize_t rc; > > char *str = buf; > > + struct tpm_chip *chip; > > + > > + rcu_read_lock(); > > + chip = dev_get_drvdata(dev); > > + if (chip) > > + get_device(chip->dev); /* protect from disappearing */ > > + rcu_read_unlock(); > > > > - struct tpm_chip *chip = dev_get_drvdata(dev); > > if (chip == NULL) > > return -ENODEV; > > > > data = kzalloc(TPM_INTERNAL_RESULT_SIZE, GFP_KERNEL); > > - if (!data) > > - return -ENOMEM; > > + if (!data) { > > + rc = -ENOMEM; > > + goto out_alloc; > > + } > > > > memcpy(data, tpm_cap, sizeof(tpm_cap)); > > data[TPM_CAP_IDX] = TPM_CAP_PROP; > > @@ -863,8 +936,8 @@ ssize_t tpm_show_caps(struct device *dev, struct device_attribute *attr, > > rc = transmit_cmd(chip, data, TPM_INTERNAL_RESULT_SIZE, > > "attempting to determine the manufacturer"); > > if (rc) { > > - kfree(data); > > - return 0; > > + rc = 0; > > + goto out; > > } > > > > str += sprintf(str, "Manufacturer: 0x%x\n", > > @@ -874,17 +947,22 @@ ssize_t tpm_show_caps(struct device *dev, struct device_attribute *attr, > > data[CAP_VERSION_IDX] = CAP_VERSION_1_1; > > rc = transmit_cmd(chip, data, TPM_INTERNAL_RESULT_SIZE, > > "attempting to determine the 1.1 version"); > > - if (rc) > > + if (rc) { > > + rc = str - buf; > > goto out; > > + } > > > > str += sprintf(str, > > "TCG version: %d.%d\nFirmware version: %d.%d\n", > > (int) data[14], (int) data[15], (int) data[16], > > (int) data[17]); > > > > + rc = str - buf; > > out: > > kfree(data); > > - return str - buf; > > +out_alloc: > > + put_device(chip->dev); > > + return rc; > > } > > EXPORT_SYMBOL_GPL(tpm_show_caps); > > > > @@ -892,16 +970,25 @@ ssize_t tpm_show_caps_1_2(struct device * dev, > > struct device_attribute * attr, char *buf) > > { > > u8 *data; > > + ssize_t rc; > > ssize_t len; > > char *str = buf; > > + struct tpm_chip *chip; > > + > > + rcu_read_lock(); > > + chip = dev_get_drvdata(dev); > > + if (chip) > > + get_device(chip->dev); /* protect from disappearing */ > > + rcu_read_unlock(); > > > > - struct tpm_chip *chip = dev_get_drvdata(dev); > > if (chip == NULL) > > return -ENODEV; > > > > data = kzalloc(TPM_INTERNAL_RESULT_SIZE, GFP_KERNEL); > > - if (!data) > > - return -ENOMEM; > > + if (!data) { > > + rc = -ENOMEM; > > + goto out_alloc; > > + } > > > > memcpy(data, tpm_cap, sizeof(tpm_cap)); > > data[TPM_CAP_IDX] = TPM_CAP_PROP; > > @@ -913,7 +1000,8 @@ ssize_t tpm_show_caps_1_2(struct device * dev, > > "attempting to determine the manufacturer\n", > > be32_to_cpu(*((__be32 *) (data + TPM_RET_CODE_IDX)))); > > kfree(data); > > - return 0; > > + rc = 0; > > + goto out; > > } > > > > str += sprintf(str, "Manufacturer: 0x%x\n", > > @@ -927,6 +1015,7 @@ ssize_t tpm_show_caps_1_2(struct device * dev, > > dev_err(chip->dev, "A TPM error (%d) occurred " > > "attempting to determine the 1.2 version\n", > > be32_to_cpu(*((__be32 *) (data + TPM_RET_CODE_IDX)))); > > + rc = str - buf; > > goto out; > > } > > str += sprintf(str, > > @@ -934,20 +1023,29 @@ ssize_t tpm_show_caps_1_2(struct device * dev, > > (int) data[16], (int) data[17], (int) data[18], > > (int) data[19]); > > > > + rc = str - buf; > > out: > > kfree(data); > > - return str - buf; > > +out_alloc: > > + put_device(chip->dev); > > + return rc; > > } > > EXPORT_SYMBOL_GPL(tpm_show_caps_1_2); > > > > ssize_t tpm_store_cancel(struct device *dev, struct device_attribute *attr, > > const char *buf, size_t count) > > { > > - struct tpm_chip *chip = dev_get_drvdata(dev); > > + struct tpm_chip *chip; > > + > > + rcu_read_lock(); > > + chip = dev_get_drvdata(dev); > > + if (chip) > > + get_device(chip->dev); /* protect from disappearing */ > > + rcu_read_unlock(); > > if (chip == NULL) > > return 0; > > - > > chip->vendor.cancel(chip); > > + put_device(chip->dev); > > return count; > > } > > EXPORT_SYMBOL_GPL(tpm_store_cancel); > > @@ -956,70 +1054,59 @@ EXPORT_SYMBOL_GPL(tpm_store_cancel); > > * Device file system interface to the TPM > > * > > * It's assured that the chip will be opened just once, > > - * by the check of is_open variable, which is protected > > - * by driver_lock. > > + * by the check of is_open variable. > > */ > > int tpm_open(struct inode *inode, struct file *file) > > { > > - int rc = 0, minor = iminor(inode); > > + int minor = iminor(inode); > > struct tpm_chip *chip = NULL, *pos; > > > > - spin_lock(&driver_lock); > > - > > - list_for_each_entry(pos, &tpm_chip_list, list) { > > + rcu_read_lock(); > > + list_for_each_entry_rcu(pos, &tpm_chip_list, list) { > > if (pos->vendor.miscdev.minor == minor) { > > chip = pos; > > + get_device(chip->dev); /* protect from disappearing */ > > break; > > } > > } > > + rcu_read_unlock(); > > + if (!chip) > > + return -ENODEV; > > > > - if (chip == NULL) { > > - rc = -ENODEV; > > - goto err_out; > > - } > > - > > - if (chip->is_open) { > > + if (!test_and_set_bit(0, &chip->is_open)) { > > dev_dbg(chip->dev, "Another process owns this TPM\n"); > > - rc = -EBUSY; > > - goto err_out; > > + return -EBUSY; > > } > > > > - chip->is_open = 1; > > - get_device(chip->dev); /* protect from chip disappearing */ > > - > > - spin_unlock(&driver_lock); > > - > > chip->data_buffer = kmalloc(TPM_BUFSIZE * sizeof(u8), GFP_KERNEL); > > if (chip->data_buffer == NULL) { > > - chip->is_open = 0; > > + clear_bit(0, &chip->is_open); > > put_device(chip->dev); > > return -ENOMEM; > > } > > > > atomic_set(&chip->data_pending, 0); > > - > > file->private_data = chip; > > return 0; > > - > > -err_out: > > - spin_unlock(&driver_lock); > > - return rc; > > } > > EXPORT_SYMBOL_GPL(tpm_open); > > > > +/* > > + * Called on file close > > + */ > > int tpm_release(struct inode *inode, struct file *file) > > { > > struct tpm_chip *chip = file->private_data; > > > > flush_scheduled_work(); > > - spin_lock(&driver_lock); > > file->private_data = NULL; > > del_singleshot_timer_sync(&chip->user_read_timer); > > atomic_set(&chip->data_pending, 0); > > - chip->is_open = 0; > > - put_device(chip->dev); > > kfree(chip->data_buffer); > > - spin_unlock(&driver_lock); > > + > > + clear_bit(0, &chip->is_open); > > + > > + put_device(chip->dev); > > return 0; > > } > > EXPORT_SYMBOL_GPL(tpm_release); > > @@ -1082,6 +1169,7 @@ ssize_t tpm_read(struct file *file, char __user *buf, > > return ret_size; > > } > > EXPORT_SYMBOL_GPL(tpm_read); > > + > > /* > > * Called on unloading the driver. > > * > > @@ -1098,13 +1186,11 @@ void tpm_remove_hardware(struct device *dev) > > } > > > > spin_lock(&driver_lock); > > - > > - list_del(&chip->list); > > - > > + list_del_rcu(&chip->list); > > spin_unlock(&driver_lock); > > + synchronize_rcu(); > > > > misc_deregister(&chip->vendor.miscdev); > > - > > sysfs_remove_group(&dev->kobj, chip->vendor.attr_group); > > tpm_bios_log_teardown(chip->bios_dir); > > > > @@ -1152,8 +1238,7 @@ EXPORT_SYMBOL_GPL(tpm_pm_resume); > > /* > > * Once all references to platform device are down to 0, > > * release all allocated structures. > > - * In case vendor provided release function, > > - * call it too. > > + * In case vendor provided release function, call it too. > > */ > > static void tpm_dev_release(struct device *dev) > > { > > @@ -1176,8 +1261,8 @@ static void tpm_dev_release(struct device *dev) > > * upon errant exit from this function specific probe function should call > > * pci_disable_device > > */ > > -struct tpm_chip *tpm_register_hardware(struct device *dev, const struct tpm_vendor_specific > > - *entry) > > +struct tpm_chip *tpm_register_hardware(struct device *dev, > > + const struct tpm_vendor_specific *entry) > > { > > #define DEVNAME_SIZE 7 > > > > @@ -1243,9 +1328,12 @@ struct tpm_chip *tpm_register_hardware(struct device *dev, const struct tpm_vend > > } > > > > chip->bios_dir = tpm_bios_log_setup(devname); > > + > > + /* Make chip available */ > > spin_lock(&driver_lock); > > - list_add(&chip->list, &tpm_chip_list); > > + list_add_rcu(&chip->list, &tpm_chip_list); > > spin_unlock(&driver_lock); > > + synchronize_rcu(); > > The above synchronize_rcu() is not needed -- unless it is required that > tpm_register_hardware() not return until it can be guaranteed that all > subsequent readers will see the new entry. (Of course, the current > CPU/task is guaranteed to see it in any subsequent call, even without > the synchronize_rcu().) > > > return chip; > > } > > -- > > 1.5.6.3 > > ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH 2/2] TPM: rcu locking 2008-08-31 20:28 ` Paul E. McKenney 2008-09-02 15:19 ` Serge E. Hallyn @ 2008-09-11 18:16 ` Mimi Zohar 1 sibling, 0 replies; 7+ messages in thread From: Mimi Zohar @ 2008-09-11 18:16 UTC (permalink / raw) To: paulmck; +Cc: Greg KH, linux-kernel, Rajiv Andrade, David Safford, Serge Hallyn On Sun, 2008-08-31 at 13:28 -0700, Paul E. McKenney wrote: > On Sat, Aug 30, 2008 at 12:05:04AM -0300, Rajiv Andrade wrote: > > Continue to protect the tpm_chip_list using the driver_lock > > as before, and add an rcu to protect readers. > > A few questions interspersed below... > > Thanx, Paul > > > Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com> > > Acked-by: Rajiv Andrade <srajiv@linux.vnet.ibm.com> > > --- > > drivers/char/tpm/tpm.c | 268 ++++++++++++++++++++++++++++++++---------------- > > 1 files changed, 178 insertions(+), 90 deletions(-) > > > > diff --git a/drivers/char/tpm/tpm.c b/drivers/char/tpm/tpm.c > > index 59b31e1..704ab01 100644 > > --- a/drivers/char/tpm/tpm.c > > +++ b/drivers/char/tpm/tpm.c > > @@ -587,14 +587,22 @@ ssize_t tpm_show_enabled(struct device * dev, struct device_attribute * attr, > > { > > u8 *data; > > ssize_t rc; > > + struct tpm_chip *chip; > > + > > The following five lines of code appear repeatedly. Why not put them > into an inline function or a macro? > > Also, doesn't there need to be an rcu_dereference() somewhere either in > this sequence of code or in either dev_get_drvdata() or get_device()? > Or am I missing something subtle here? > > >From what I see of the code, I actually don't understand why the > rcu_read_lock() is needed here -- only tpm_chip_list is covered by > the RCU list addition/deletion primitives in this patch. If you are > adding a multilinked data structure into an RCU-protected list, you > need RCU traversal primitives only when traversing the list, not the > data structure contained in the list. (Of course, any changes to the > data structure contained in the list must be protected somehow or other, > unless there are no such changes.) > > > + rcu_read_lock(); > > + chip = dev_get_drvdata(dev); > > + if (chip) > > + get_device(chip->dev); /* protect from disappearing */ > > + rcu_read_unlock(); > > > > - struct tpm_chip *chip = dev_get_drvdata(dev); > > if (chip == NULL) > > return -ENODEV; > > > > data = kzalloc(TPM_INTERNAL_RESULT_SIZE, GFP_KERNEL); > > - if (!data) > > - return -ENOMEM; > > + if (!data) { > > + rc = -ENOMEM; > > + goto out_alloc; > > + } > > > > memcpy(data, tpm_cap, sizeof(tpm_cap)); > > data[TPM_CAP_IDX] = TPM_CAP_FLAG; Ok, the rcu_read_lock is only used when accessing an rcu protected variable, such as when walking the tpm_chip_list. When registering the tpm chip, a pointer to the chip is stored in device->driver_data. The tpm_show_XXX() functions dereference and use it, which is safe if the device is pinned when the sysfs file is opened. Documentation indicates that the kobject is protected from going away when attribute files are opened. I'm not seeing the kobject refcount being incremented, when the attribute file is opened. How is the device being pinned? Thanks! Mimi Zohar ^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2008-09-11 18:17 UTC | newest] Thread overview: 7+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2008-08-30 3:05 [PATCH 0/2] TPM Rajiv Andrade 2008-08-30 3:05 ` [PATCH 1/2] TPM: update char dev BKL pushdown Rajiv Andrade 2008-09-02 15:03 ` Serge E. Hallyn 2008-08-30 3:05 ` [PATCH 2/2] TPM: rcu locking Rajiv Andrade 2008-08-31 20:28 ` Paul E. McKenney 2008-09-02 15:19 ` Serge E. Hallyn 2008-09-11 18:16 ` Mimi Zohar
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