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| author |   Gustavo A. R. Silva <gustavoars@kernel.org> | 2020-05-07 14:21:41 -0500 |
|---|---|---|
| committer |   Peter Zijlstra <peterz@infradead.org> | 2020-05-19 20:34:14 +0200 |
| commit | 04f5c362ec6d3ff0e14f1c05230b550da7f528a4 (patch) | |
| tree | d21f39df3f6ae8d34991697ab8aad138ccd75812 /kernel/sched | |
| parent | sched/pelt: Sync util/runnable_sum with PELT window when propagating (diff) | |
| download | wireguard-linux-04f5c362ec6d3ff0e14f1c05230b550da7f528a4.tar.xz wireguard-linux-04f5c362ec6d3ff0e14f1c05230b550da7f528a4.zip | |
sched/fair: Replace zero-length array with flexible-array
The current codebase makes use of the zero-length array language
extension to the C90 standard, but the preferred mechanism to declare
variable-length types such as these ones is a flexible array member[1][2],
introduced in C99:
struct foo {
int stuff;
struct boo array[];
};
By making use of the mechanism above, we will get a compiler warning
in case the flexible array does not occur last in the structure, which
will help us prevent some kind of undefined behavior bugs from being
inadvertently introduced[3] to the codebase from now on.
Also, notice that, dynamic memory allocations won't be affected by
this change:
"Flexible array members have incomplete type, and so the sizeof operator
may not be applied. As a quirk of the original implementation of
zero-length arrays, sizeof evaluates to zero."[1]
sizeof(flexible-array-member) triggers a warning because flexible array
members have incomplete type[1]. There are some instances of code in
which the sizeof operator is being incorrectly/erroneously applied to
zero-length arrays and the result is zero. Such instances may be hiding
some bugs. So, this work (flexible-array member conversions) will also
help to get completely rid of those sorts of issues.
This issue was found with the help of Coccinelle.
[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://github.com/KSPP/linux/issues/21
[3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour")
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200507192141.GA16183@embeddedor
Diffstat (limited to 'kernel/sched')
| -rw-r--r-- | kernel/sched/fair.c | 2 | ||||
| -rw-r--r-- | kernel/sched/sched.h | 2 |
2 files changed, 2 insertions, 2 deletions
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 44b0c8edc260..01f94cf52783 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -1094,7 +1094,7 @@ struct numa_group { * more by CPU use than by memory faults. */ unsigned long *faults_cpu; - unsigned long faults[0]; + unsigned long faults[]; }; /* diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 21416b30c520..2bd2a222318a 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -1462,7 +1462,7 @@ struct sched_group { * by attaching extra space to the end of the structure, * depending on how many CPUs the kernel has booted up with) */ - unsigned long cpumask[0]; + unsigned long cpumask[]; }; static inline struct cpumask *sched_group_span(struct sched_group *sg) |