eal: explicit cast in rwlock functions

GCC 8.1 warned:

In function 'rte_rwlock_read_lock':
rte_rwlock.h:74:12: warning: conversion to 'uint32_t'
{aka 'unsigned int'} from 'int32_t' {aka 'int'} may
change the sign of the result [-Wsign-conversion]
            x, x + 1);
            ^
rte_rwlock.h:74:17: warning: conversion to 'uint32_t'
{aka 'unsigned int'} from 'int' may change the sign
of the result [-Wsign-conversion]
            x, x + 1);
               ~~^~~

In function 'rte_rwlock_write_lock':
rte_rwlock.h:110:15: warning: unsigned conversion
from 'int' to 'uint32_t' {aka 'unsigned int'}
changes value from '-1' to '4294967295' [-Wsign-conversion]
            0, -1);
               ^~

Again in this case we are making explicit the exact cast
that was always happening implicitly.  The patch does not
change the generated code.

The int32_t temp "x" is required to be signed to detect
a < 0 error condition from the lock status.  Afterwards,
it has always been implicitly cast to uint32_t when it
is used in the arguments to rte_atomic32_cmpset()...
gcc8.1 objects to the implicit cast now and requires us
to cast it explicitly.

Fixes: af75078fec ("first public release")
Cc: stable@dpdk.org
Signed-off-by: Andy Green <andy@warmcat.com>
Acked-by: Bruce Richardson <bruce.richardson@intel.com>

diff --git a/lib/librte_eal/common/include/generic/rte_rwlock.h b/lib/librte_eal/common/include/generic/rte_rwlock.h
index 899e9bc..5751a0e 100644 (file)
--- a/lib/librte_eal/common/include/generic/rte_rwlock.h
+++ b/lib/librte_eal/common/include/generic/rte_rwlock.h
@@ -71,7 +71,7 @@ rte_rwlock_read_lock(rte_rwlock_t *rwl)
                        continue;
                }
                success = rte_atomic32_cmpset((volatile uint32_t *)&rwl->cnt,
-                                             x, x + 1);
+                                             (uint32_t)x, (uint32_t)(x + 1));
        }
 }
 
@@ -107,7 +107,7 @@ rte_rwlock_write_lock(rte_rwlock_t *rwl)
                        continue;
                }
                success = rte_atomic32_cmpset((volatile uint32_t *)&rwl->cnt,
-                                             0, -1);
+                                             0, (uint32_t)-1);
        }
 }