From: Arnd Bergmann <arnd@arndb.de> To: Ross Zwisler <ross.zwisler@linux.intel.com>, Andrew Morton <akpm@linux-foundation.org>, Dan Williams <dan.j.williams@intel.com> Cc: Arnd Bergmann <arnd@arndb.de>, linux-nvdimm@lists.01.org, linux-kernel@vger.kernel.org, Christoph Hellwig <hch@infradead.org> Subject: [PATCH] nvdimm: avoid bogus -Wmaybe-uninitialized warning Date: Tue, 1 Aug 2017 13:48:48 +0200 [thread overview] Message-ID: <20170801114926.1171418-1-arnd@arndb.de> (raw) Removing the btt_rw_page/pmem_rw_page functions had a surprising side-effect of introducing a false-positive warning in another function, due to changed inlining decisions in gcc: In file included from drivers/nvdimm/pmem.c:36:0: drivers/nvdimm/pmem.c: In function 'pmem_make_request': drivers/nvdimm/nd.h:407:2: error: 'start' may be used uninitialized in this function [-Werror=maybe-uninitialized] drivers/nvdimm/pmem.c:174:16: note: 'start' was declared here In file included from drivers/nvdimm/btt.c:27:0: drivers/nvdimm/btt.c: In function 'btt_make_request': drivers/nvdimm/nd.h:407:2: error: 'start' may be used uninitialized in this function [-Werror=maybe-uninitialized] drivers/nvdimm/btt.c:1202:16: note: 'start' was declared here The problem is that gcc fails to track the value of the 'do_acct' variable here and has to read it back from stack, but it does remember that 'start' may be uninitialized sometimes. This shuts up the warning by making nd_iostat_start() always initialize the 'start' variable. In those cases that gcc successfully tracks the state of the variable, this will have no effect. Fixes: 503a5e89b1de ("drivers/nvdimm/btt.c: remove btt_rw_page()") Fixes: 58100d6e735e ("drivers/nvdimm/pmem.c: remove pmem_rw_page()") Signed-off-by: Arnd Bergmann <arnd@arndb.de> --- drivers/nvdimm/nd.h | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/nvdimm/nd.h b/drivers/nvdimm/nd.h index e1b5715bd91f..64f79a156456 100644 --- a/drivers/nvdimm/nd.h +++ b/drivers/nvdimm/nd.h @@ -392,8 +392,10 @@ static inline bool nd_iostat_start(struct bio *bio, unsigned long *start) { struct gendisk *disk = bio->bi_bdev->bd_disk; - if (!blk_queue_io_stat(disk->queue)) + if (!blk_queue_io_stat(disk->queue)) { + *start = 0; return false; + } *start = jiffies; generic_start_io_acct(bio_data_dir(bio), -- 2.9.0 _______________________________________________ Linux-nvdimm mailing list Linux-nvdimm@lists.01.org https://lists.01.org/mailman/listinfo/linux-nvdimm
WARNING: multiple messages have this Message-ID (diff)
From: Arnd Bergmann <arnd@arndb.de> To: Ross Zwisler <ross.zwisler@linux.intel.com>, Andrew Morton <akpm@linux-foundation.org>, Dan Williams <dan.j.williams@intel.com> Cc: Christoph Hellwig <hch@infradead.org>, Arnd Bergmann <arnd@arndb.de>, Vishal Verma <vishal.l.verma@intel.com>, Toshi Kani <toshi.kani@hpe.com>, Johannes Thumshirn <jthumshirn@suse.de>, linux-nvdimm@lists.01.org, linux-kernel@vger.kernel.org Subject: [PATCH] nvdimm: avoid bogus -Wmaybe-uninitialized warning Date: Tue, 1 Aug 2017 13:48:48 +0200 [thread overview] Message-ID: <20170801114926.1171418-1-arnd@arndb.de> (raw) Removing the btt_rw_page/pmem_rw_page functions had a surprising side-effect of introducing a false-positive warning in another function, due to changed inlining decisions in gcc: In file included from drivers/nvdimm/pmem.c:36:0: drivers/nvdimm/pmem.c: In function 'pmem_make_request': drivers/nvdimm/nd.h:407:2: error: 'start' may be used uninitialized in this function [-Werror=maybe-uninitialized] drivers/nvdimm/pmem.c:174:16: note: 'start' was declared here In file included from drivers/nvdimm/btt.c:27:0: drivers/nvdimm/btt.c: In function 'btt_make_request': drivers/nvdimm/nd.h:407:2: error: 'start' may be used uninitialized in this function [-Werror=maybe-uninitialized] drivers/nvdimm/btt.c:1202:16: note: 'start' was declared here The problem is that gcc fails to track the value of the 'do_acct' variable here and has to read it back from stack, but it does remember that 'start' may be uninitialized sometimes. This shuts up the warning by making nd_iostat_start() always initialize the 'start' variable. In those cases that gcc successfully tracks the state of the variable, this will have no effect. Fixes: 503a5e89b1de ("drivers/nvdimm/btt.c: remove btt_rw_page()") Fixes: 58100d6e735e ("drivers/nvdimm/pmem.c: remove pmem_rw_page()") Signed-off-by: Arnd Bergmann <arnd@arndb.de> --- drivers/nvdimm/nd.h | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/nvdimm/nd.h b/drivers/nvdimm/nd.h index e1b5715bd91f..64f79a156456 100644 --- a/drivers/nvdimm/nd.h +++ b/drivers/nvdimm/nd.h @@ -392,8 +392,10 @@ static inline bool nd_iostat_start(struct bio *bio, unsigned long *start) { struct gendisk *disk = bio->bi_bdev->bd_disk; - if (!blk_queue_io_stat(disk->queue)) + if (!blk_queue_io_stat(disk->queue)) { + *start = 0; return false; + } *start = jiffies; generic_start_io_acct(bio_data_dir(bio), -- 2.9.0
next reply other threads:[~2017-08-01 11:47 UTC|newest] Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top 2017-08-01 11:48 Arnd Bergmann [this message] 2017-08-01 11:48 ` [PATCH] nvdimm: avoid bogus -Wmaybe-uninitialized warning Arnd Bergmann 2017-08-01 18:00 ` Ross Zwisler 2017-08-01 18:00 ` Ross Zwisler 2017-08-01 18:07 ` Dan Williams 2017-08-01 18:07 ` Dan Williams 2017-08-01 21:45 ` Andrew Morton 2017-08-01 21:45 ` Andrew Morton 2017-08-01 22:23 ` Ross Zwisler 2017-08-01 22:23 ` Ross Zwisler 2017-08-02 10:54 ` Arnd Bergmann 2017-08-02 10:54 ` Arnd Bergmann
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