[PATCH v2 00/13] Introduce seqnum_ops

[PATCH v2 00/13] Introduce seqnum_ops

[Shuah Khan]

Sequence Number api provides interfaces for unsigned atomic up counters
leveraging atomic_t and atomic64_t ops underneath.

There are a number of atomic_t usages in the kernel where atomic_t api
is used for counting sequence numbers and other statistical counters.
Several of these usages, convert atomic_read() and atomic_inc_return()
return values to unsigned. Introducing sequence number ops supports
these use-cases with a standard core-api.

The atomic_t api provides a wide range of atomic operations as a base
api to implement atomic counters, bitops, spinlock interfaces. The usages
also evolved into being used for resource lifetimes and state management.
The refcount_t api was introduced to address resource lifetime problems
related to atomic_t wrapping. There is a large overlap between the
atomic_t api used for resource lifetimes and just counters, stats, and
sequence numbers. It has become difficult to differentiate between the
atomic_t usages that should be converted to refcount_t and the ones that
can be left alone. Introducing seqnum_ops to wrap the usages that are
stats, counters, sequence numbers makes it easier for tools that scan
for underflow and overflow on atomic_t usages to detect overflow and
underflows to scan just the cases that are prone to errors.

In addition, to supporting sequence number use-cases, Sequence Number Ops
helps differentiate atomic_t counter usages from atomic_t usages that guard
object lifetimes, hence prone to overflow and underflow errors from up
counting use-cases. It becomes easier for tools that scan for underflow and
overflow on atomic_t usages to detect overflow and underflows to scan just
the cases that are prone to errors.

Changes since v1:
- Removed dec based on Greg KH's comments
- Removed read/set/inc based on the discussion with Peter Zijlstra
- Interfaces are restricted to init, increment and return new value,
  and fetch current value.
- Interfaces return u32 and u64 - a few reviewers suggested unsigned.
  After reviewing a few use-cases, I determined this is a good path
  forward. It adds unsigned atomic support that doesn't exist now,
  and simplifies code in drivers that currently convert atomic_t return
  values to unsigned. All the drivers changes included in this series
  used to convert atomic_t returns to unsigned.

Patch v1 thread:
https://lore.kernel.org/lkml/cover.1605027593.git.skhan@linuxfoundation.org/

Counters thread:
lore.kernel.org/lkml/cover.1602209970.git.skhan@linuxfoundation.org

Shuah Khan (13):
  seqnum_ops: Introduce Sequence Number Ops
  selftests: lib:test_seqnum_ops: add new test for seqnum_ops
  drivers/acpi: convert seqno seqnum_ops
  drivers/acpi/apei: convert seqno to seqnum_ops
  drivers/base/test/test_async_driver_probe: convert to use seqnum_ops
  drivers/char/ipmi: convert stats to use seqnum_ops
  drivers/edac: convert pci counters to seqnum_ops
  drivers/oprofile: convert stats to use seqnum_ops
  drivers/staging/rtl8723bs: convert stats to use seqnum_ops
  usb: usbip/vhci: convert seqno to seqnum_ops
  drivers/staging/rtl8188eu: convert stats to use seqnum_ops
  drivers/staging/unisys/visorhba: convert stats to use seqnum_ops
  security/integrity/ima: converts stats to seqnum_ops

 Documentation/core-api/atomic_ops.rst         |   4 +
 Documentation/core-api/index.rst              |   1 +
 Documentation/core-api/seqnum_ops.rst         |  89 +++++++++++++
 MAINTAINERS                                   |   8 ++
 drivers/acpi/acpi_extlog.c                    |   8 +-
 drivers/acpi/apei/ghes.c                      |   8 +-
 drivers/base/test/test_async_driver_probe.c   |  28 +++--
 drivers/char/ipmi/ipmi_msghandler.c           |   9 +-
 drivers/char/ipmi/ipmi_si_intf.c              |   9 +-
 drivers/char/ipmi/ipmi_ssif.c                 |   9 +-
 drivers/edac/edac_pci.h                       |   5 +-
 drivers/edac/edac_pci_sysfs.c                 |  30 ++---
 drivers/oprofile/buffer_sync.c                |   9 +-
 drivers/oprofile/event_buffer.c               |   3 +-
 drivers/oprofile/oprof.c                      |   3 +-
 drivers/oprofile/oprofile_stats.c             |  11 +-
 drivers/oprofile/oprofile_stats.h             |  11 +-
 drivers/oprofile/oprofilefs.c                 |   3 +-
 drivers/staging/rtl8188eu/core/rtw_mlme_ext.c |  23 +++-
 .../staging/rtl8188eu/include/rtw_mlme_ext.h  |   3 +-
 drivers/staging/rtl8723bs/core/rtw_cmd.c      |   3 +-
 drivers/staging/rtl8723bs/core/rtw_mlme_ext.c |  33 +++--
 drivers/staging/rtl8723bs/include/rtw_cmd.h   |   3 +-
 .../staging/rtl8723bs/include/rtw_mlme_ext.h  |   3 +-
 .../staging/unisys/visorhba/visorhba_main.c   |  21 ++--
 drivers/usb/usbip/vhci.h                      |   3 +-
 drivers/usb/usbip/vhci_hcd.c                  |   7 +-
 drivers/usb/usbip/vhci_rx.c                   |   5 +-
 include/linux/oprofile.h                      |   3 +-
 include/linux/seqnum_ops.h                    | 118 +++++++++++++++++
 lib/Kconfig                                   |   9 ++
 lib/Makefile                                  |   1 +
 lib/test_seqnum_ops.c                         | 119 ++++++++++++++++++
 security/integrity/ima/ima.h                  |   5 +-
 security/integrity/ima/ima_api.c              |   3 +-
 security/integrity/ima/ima_fs.c               |   5 +-
 security/integrity/ima/ima_queue.c            |   7 +-
 tools/testing/selftests/lib/Makefile          |   1 +
 tools/testing/selftests/lib/config            |   1 +
 .../testing/selftests/lib/test_seqnum_ops.sh  |  10 ++
 40 files changed, 524 insertions(+), 110 deletions(-)
 create mode 100644 Documentation/core-api/seqnum_ops.rst
 create mode 100644 include/linux/seqnum_ops.h
 create mode 100644 lib/test_seqnum_ops.c
 create mode 100755 tools/testing/selftests/lib/test_seqnum_ops.sh

-- 
2.27.0

[PATCH v2 07/13] drivers/edac: convert pci counters to seqnum_ops

[Shuah Khan]

Sequence Number api provides interfaces for unsigned atomic up counters
leveraging atomic_t and atomic64_t ops underneath.

atomic_t variables used for pci counters keep track of pci parity and
non-parity errors. Convert them to use seqnum_ops.

Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
---
 drivers/edac/edac_pci.h       |  5 +++--
 drivers/edac/edac_pci_sysfs.c | 30 +++++++++++++++---------------
 2 files changed, 18 insertions(+), 17 deletions(-)

diff --git a/drivers/edac/edac_pci.h b/drivers/edac/edac_pci.h
index 5175f5724cfa..33b33e62c37f 100644
--- a/drivers/edac/edac_pci.h
+++ b/drivers/edac/edac_pci.h
@@ -30,12 +30,13 @@
 #include <linux/pci.h>
 #include <linux/types.h>
 #include <linux/workqueue.h>
+#include <linux/seqnum_ops.h>
 
 #ifdef CONFIG_PCI
 
 struct edac_pci_counter {
-	atomic_t pe_count;
-	atomic_t npe_count;
+	struct seqnum32 pe_count;
+	struct seqnum32 npe_count;
 };
 
 /*
diff --git a/drivers/edac/edac_pci_sysfs.c b/drivers/edac/edac_pci_sysfs.c
index 53042af7262e..08a34ecd2fb7 100644
--- a/drivers/edac/edac_pci_sysfs.c
+++ b/drivers/edac/edac_pci_sysfs.c
@@ -23,8 +23,8 @@ static int edac_pci_log_pe = 1;		/* log PCI parity errors */
 static int edac_pci_log_npe = 1;	/* log PCI non-parity error errors */
 static int edac_pci_poll_msec = 1000;	/* one second workq period */
 
-static atomic_t pci_parity_count = ATOMIC_INIT(0);
-static atomic_t pci_nonparity_count = ATOMIC_INIT(0);
+static struct seqnum32 pci_parity_count = SEQNUM_INIT(0);
+static struct seqnum32 pci_nonparity_count = SEQNUM_INIT(0);
 
 static struct kobject *edac_pci_top_main_kobj;
 static atomic_t edac_pci_sysfs_refcount = ATOMIC_INIT(0);
@@ -58,13 +58,13 @@ int edac_pci_get_poll_msec(void)
 /**************************** EDAC PCI sysfs instance *******************/
 static ssize_t instance_pe_count_show(struct edac_pci_ctl_info *pci, char *data)
 {
-	return sprintf(data, "%u\n", atomic_read(&pci->counters.pe_count));
+	return sprintf(data, "%u\n", seqnum32_fetch(&pci->counters.pe_count));
 }
 
 static ssize_t instance_npe_count_show(struct edac_pci_ctl_info *pci,
 				char *data)
 {
-	return sprintf(data, "%u\n", atomic_read(&pci->counters.npe_count));
+	return sprintf(data, "%u\n", seqnum32_fetch(&pci->counters.npe_count));
 }
 
 #define to_instance(k) container_of(k, struct edac_pci_ctl_info, kobj)
@@ -553,7 +553,7 @@ static void edac_pci_dev_parity_test(struct pci_dev *dev)
 			edac_printk(KERN_CRIT, EDAC_PCI,
 				"Signaled System Error on %s\n",
 				pci_name(dev));
-			atomic_inc(&pci_nonparity_count);
+			seqnum32_inc_return(&pci_nonparity_count);
 		}
 
 		if (status & (PCI_STATUS_PARITY)) {
@@ -561,7 +561,7 @@ static void edac_pci_dev_parity_test(struct pci_dev *dev)
 				"Master Data Parity Error on %s\n",
 				pci_name(dev));
 
-			atomic_inc(&pci_parity_count);
+			seqnum32_inc_return(&pci_parity_count);
 		}
 
 		if (status & (PCI_STATUS_DETECTED_PARITY)) {
@@ -569,7 +569,7 @@ static void edac_pci_dev_parity_test(struct pci_dev *dev)
 				"Detected Parity Error on %s\n",
 				pci_name(dev));
 
-			atomic_inc(&pci_parity_count);
+			seqnum32_inc_return(&pci_parity_count);
 		}
 	}
 
@@ -592,7 +592,7 @@ static void edac_pci_dev_parity_test(struct pci_dev *dev)
 				edac_printk(KERN_CRIT, EDAC_PCI, "Bridge "
 					"Signaled System Error on %s\n",
 					pci_name(dev));
-				atomic_inc(&pci_nonparity_count);
+				seqnum32_inc_return(&pci_nonparity_count);
 			}
 
 			if (status & (PCI_STATUS_PARITY)) {
@@ -600,7 +600,7 @@ static void edac_pci_dev_parity_test(struct pci_dev *dev)
 					"Master Data Parity Error on "
 					"%s\n", pci_name(dev));
 
-				atomic_inc(&pci_parity_count);
+				seqnum32_inc_return(&pci_parity_count);
 			}
 
 			if (status & (PCI_STATUS_DETECTED_PARITY)) {
@@ -608,7 +608,7 @@ static void edac_pci_dev_parity_test(struct pci_dev *dev)
 					"Detected Parity Error on %s\n",
 					pci_name(dev));
 
-				atomic_inc(&pci_parity_count);
+				seqnum32_inc_return(&pci_parity_count);
 			}
 		}
 	}
@@ -638,7 +638,7 @@ static inline void edac_pci_dev_parity_iterator(pci_parity_check_fn_t fn)
  */
 void edac_pci_do_parity_check(void)
 {
-	int before_count;
+	u32 before_count;
 
 	edac_dbg(3, "\n");
 
@@ -646,7 +646,7 @@ void edac_pci_do_parity_check(void)
 	if (!check_pci_errors)
 		return;
 
-	before_count = atomic_read(&pci_parity_count);
+	before_count = seqnum32_fetch(&pci_parity_count);
 
 	/* scan all PCI devices looking for a Parity Error on devices and
 	 * bridges.
@@ -658,7 +658,7 @@ void edac_pci_do_parity_check(void)
 	/* Only if operator has selected panic on PCI Error */
 	if (edac_pci_get_panic_on_pe()) {
 		/* If the count is different 'after' from 'before' */
-		if (before_count != atomic_read(&pci_parity_count))
+		if (before_count != seqnum32_fetch(&pci_parity_count))
 			panic("EDAC: PCI Parity Error");
 	}
 }
@@ -686,7 +686,7 @@ void edac_pci_handle_pe(struct edac_pci_ctl_info *pci, const char *msg)
 {
 
 	/* global PE counter incremented by edac_pci_do_parity_check() */
-	atomic_inc(&pci->counters.pe_count);
+	seqnum32_inc_return(&pci->counters.pe_count);
 
 	if (edac_pci_get_log_pe())
 		edac_pci_printk(pci, KERN_WARNING,
@@ -711,7 +711,7 @@ void edac_pci_handle_npe(struct edac_pci_ctl_info *pci, const char *msg)
 {
 
 	/* global NPE counter incremented by edac_pci_do_parity_check() */
-	atomic_inc(&pci->counters.npe_count);
+	seqnum32_inc_return(&pci->counters.npe_count);
 
 	if (edac_pci_get_log_npe())
 		edac_pci_printk(pci, KERN_WARNING,
-- 
2.27.0