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blk-mq: silence false positive warnings in hctx_unlock() 

In some stupider versions of gcc, it complains:

block/blk-mq.c: In function ‘blk_mq_complete_request’:
./include/linux/srcu.h:175:2: warning: ‘srcu_idx’ may be used uninitialized in this function [-Wmaybe-uninitialized]
  __srcu_read_unlock(sp, idx);
  ^
block/blk-mq.c:620:6: note: ‘srcu_idx’ was declared here
  int srcu_idx;
      ^

which is completely bogus, since we only use srcu_idx when
hctx->flags & BLK_MQ_F_BLOCKING is set, and that's the case where
hctx_lock() has initialized it.

Just set it to '0' in the normal path in hctx_lock() to silence
this annoying warning.

Fixes: 04ced159ce ("blk-mq: move hctx lock/unlock into a helper")
Fixes: 5197c05e16 ("blk-mq: protect completion path with RCU")
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe 2018-01-09 09:32:25 -07:00
parent 05707b64ae
commit 08b5a6e2a7
1 changed files with 4 additions and 2 deletions
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6
block/blk-mq.c
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@ -569,9 +569,11 @@ static void hctx_unlock(struct blk_mq_hw_ctx *hctx, int srcu_idx)
static void hctx_lock(struct blk_mq_hw_ctx *hctx, int *srcu_idx)
{
if (!(hctx->flags & BLK_MQ_F_BLOCKING))
if (!(hctx->flags & BLK_MQ_F_BLOCKING)) {
/* shut up gcc false positive */
*srcu_idx = 0;
rcu_read_lock();
else
} else
*srcu_idx = srcu_read_lock(hctx->srcu);
}