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De Francesco" To: Peter Zijlstra , dan.j.williams@intel.com, linux-kernel@vger.kernel.org, Ingo Molnar , linux-cxl@vger.kernel.org Cc: "Fabio M. De Francesco" , Ira Weiny Subject: [RFC PATCH v3] cleanup: Add cond_guard() to conditional guards Date: Wed, 31 Jan 2024 14:37:35 +0100 Message-ID: <20240131134108.423258-1-fabio.maria.de.francesco@linux.intel.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-cxl@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 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 Cc: Dan Williams Suggested-by: Ira Weiny Signed-off-by: Fabio M. De Francesco --- 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)