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Message-ID: <20240131134108.423258-1-fabio.maria.de.francesco@linux.intel.com>
Date: Wed, 31 Jan 2024 14:37:35 +0100
From: "Fabio M. De Francesco" <fabio.maria.de.francesco@...ux.intel.com>
To: Peter Zijlstra <peterz@...radead.org>,
dan.j.williams@...el.com,
linux-kernel@...r.kernel.org,
Ingo Molnar <mingo@...nel.org>,
linux-cxl@...r.kernel.org
Cc: "Fabio M. De Francesco" <fabio.maria.de.francesco@...ux.intel.com>,
Ira Weiny <ira.weiny@...el.com>
Subject: [RFC PATCH v3] cleanup: Add cond_guard() to conditional guards
Add cond_guard() to conditional guards.
cond_guard() is used for the _interruptible(), _killable(), and _try
versions of locks.
It stores a return value to a variable whose address is given to its
second argument, that is either '-1' on failure or '0' on success to
acquire a lock. The returned value can be checked to act accordingly
(e.g., to call printk() and return -EINTR in case of failure of an
_interruptible() variant)
As the other guards, it avoids to open code the release of the lock
after a goto to an 'out' label.
This remains an RFC because Dan suggested a slightly different syntax.
The changes to the CXL code are provided only to show the use of this
macro. If consensus is gathered on this macro, the cleanup of
show_targetN() will be submitted later in a separate patch.
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Dan Williams <dan.j.williams@...el.com>
Suggested-by: Ira Weiny <ira.weiny@...el.com>
Signed-off-by: Fabio M. De Francesco <fabio.maria.de.francesco@...ux.intel.com>
---
Changes from v1 and v2:
I've taken into account Dan's comments (thanks).
drivers/cxl/core/region.c | 15 +++++----------
include/linux/cleanup.h | 19 +++++++++++++++++++
2 files changed, 24 insertions(+), 10 deletions(-)
diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
index 0f05692bfec3..560f25bdfd11 100644
--- a/drivers/cxl/core/region.c
+++ b/drivers/cxl/core/region.c
@@ -668,26 +668,21 @@ static size_t show_targetN(struct cxl_region *cxlr, char *buf, int pos)
struct cxl_endpoint_decoder *cxled;
int rc;
- rc = down_read_interruptible(&cxl_region_rwsem);
+ cond_guard(rwsem_read_intr, &rc, &cxl_region_rwsem);
if (rc)
- return rc;
+ return -EINTR;
if (pos >= p->interleave_ways) {
dev_dbg(&cxlr->dev, "position %d out of range %d\n", pos,
p->interleave_ways);
- rc = -ENXIO;
- goto out;
+ return -ENXIO;
}
cxled = p->targets[pos];
if (!cxled)
- rc = sysfs_emit(buf, "\n");
+ return sysfs_emit(buf, "\n");
else
- rc = sysfs_emit(buf, "%s\n", dev_name(&cxled->cxld.dev));
-out:
- up_read(&cxl_region_rwsem);
-
- return rc;
+ return sysfs_emit(buf, "%s\n", dev_name(&cxled->cxld.dev));
}
static int match_free_decoder(struct device *dev, void *data)
diff --git a/include/linux/cleanup.h b/include/linux/cleanup.h
index c2d09bc4f976..a4b40d511f9e 100644
--- a/include/linux/cleanup.h
+++ b/include/linux/cleanup.h
@@ -134,6 +134,20 @@ static inline class_##_name##_t class_##_name##ext##_constructor(_init_args) \
* an anonymous instance of the (guard) class, not recommended for
* conditional locks.
*
+ * cond_guard(name, ret, args...):
+ * for conditional locks like mutex_trylock() or down_read_interruptible().
+ * 'ret' is a pointer to a variable where this macro stores 0 on success
+ * and -1 on failure to acquire a lock.
+ *
+ * Example:
+ *
+ * int ret;
+ * cond_guard(rwsem_read_try, &ret, &sem);
+ * if (ret) {
+ * dev_dbg("down_read_trylock() failed to down 'sem')\n");
+ * return 0; // down_read_trylock() returns 0 on contention
+ * }
+ *
* scoped_guard (name, args...) { }:
* similar to CLASS(name, scope)(args), except the variable (with the
* explicit name 'scope') is declard in a for-loop such that its scope is
@@ -165,6 +179,11 @@ static inline class_##_name##_t class_##_name##ext##_constructor(_init_args) \
#define __guard_ptr(_name) class_##_name##_lock_ptr
+#define cond_guard(_name, _ret, args...) \
+ CLASS(_name, scope)(args); \
+ if (!__guard_ptr(_name)(&scope)) *_ret = -1 \
+ else *_ret = 0
+
#define scoped_guard(_name, args...) \
for (CLASS(_name, scope)(args), \
*done = NULL; __guard_ptr(_name)(&scope) && !done; done = (void *)1)
--
2.43.0
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