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smp: Fix smp_call_function_single_async prototype

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As of commit 966a967116 ("smp: Avoid using two cache lines for struct
call_single_data"), the smp code prefers 32-byte aligned call_single_data
objects for performance reasons, but the block layer includes an instance
of this structure in the main 'struct request' that is more senstive
to size than to performance here, see 4ccafe0320 ("block: unalign
call_single_data in struct request").

The result is a violation of the calling conventions that clang correctly
points out:

block/blk-mq.c:630:39: warning: passing 8-byte aligned argument to 32-byte aligned parameter 2 of 'smp_call_function_single_async' may result in an unaligned pointer access [-Walign-mismatch]
                smp_call_function_single_async(cpu, &rq->csd);

It does seem that the usage of the call_single_data without cache line
alignment should still be allowed by the smp code, so just change the
function prototype so it accepts both, but leave the default alignment
unchanged for the other users. This seems better to me than adding
a local hack to shut up an otherwise correct warning in the caller.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Jens Axboe <axboe@kernel.dk>
Link: https://lkml.kernel.org/r/20210505211300.3174456-1-arnd@kernel.org
This commit is contained in:
Arnd Bergmann
2021-05-05 23:12:42 +02:00
committed by Peter Zijlstra
parent 635de956a7
commit 1139aeb1c5
3 changed files with 15 additions and 15 deletions
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2
include/linux/smp.h
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@@ -53,7 +53,7 @@ int smp_call_function_single(int cpuid, smp_call_func_t func, void *info,
void on_each_cpu_cond_mask(smp_cond_func_t cond_func, smp_call_func_t func,
void *info, bool wait, const struct cpumask *mask);
int smp_call_function_single_async(int cpu, call_single_data_t *csd);
int smp_call_function_single_async(int cpu, struct __call_single_data *csd);
/*
* Call a function on all processors