[PATCH] ipc: Remove dead code in perform_atomic_semop()

[PATCH] ipc: Remove dead code in perform_atomic_semop()

[Gautam Menghani]

Remove the line which is dead code. Fixes the clang scan warning:
warning: Value stored to 'result' is never read [deadcode.DeadStores]
                result = curr->semval;

Signed-off-by: Gautam Menghani <gautammenghani201@gmail.com>
---
 ipc/sem.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/ipc/sem.c b/ipc/sem.c
index 0dbdb98fdf2d..156824bcda47 100644
--- a/ipc/sem.c
+++ b/ipc/sem.c
@@ -766,7 +766,6 @@ static int perform_atomic_semop(struct sem_array *sma, struct sem_queue *q)
 	for (sop = sops; sop < sops + nsops; sop++) {
 		curr = &sma->sems[sop->sem_num];
 		sem_op = sop->sem_op;
-		result = curr->semval;
 
 		if (sop->sem_flg & SEM_UNDO) {
 			int undo = un->semadj[sop->sem_num] - sem_op;
-- 
2.25.1

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Re: [PATCH] ipc: Remove dead code in perform_atomic_semop()

[vasily.averin]

On 5/24/22 21:22, Gautam Menghani wrote:
> Remove the line which is dead code. Fixes the clang scan warning:
> warning: Value stored to 'result' is never read [deadcode.DeadStores]
>                 result = curr->semval;
> 
> Signed-off-by: Gautam Menghani <gautammenghani201@gmail.com>
> ---
>  ipc/sem.c | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/ipc/sem.c b/ipc/sem.c
> index 0dbdb98fdf2d..156824bcda47 100644
> --- a/ipc/sem.c
> +++ b/ipc/sem.c
> @@ -766,7 +766,6 @@ static int perform_atomic_semop(struct sem_array *sma, struct sem_queue *q)
>  	for (sop = sops; sop < sops + nsops; sop++) {
>  		curr = &sma->sems[sop->sem_num];
>  		sem_op = sop->sem_op;
> -		result = curr->semval;
>  
>  		if (sop->sem_flg & SEM_UNDO) {
>  			int undo = un->semadj[sop->sem_num] - sem_op;

Perhaps it would be better to keep the "result" but use it in the
marked line below, like it was done in previous part of this function?

                        un->semadj[sop->sem_num] = undo;
                }
                curr->semval += sem_op; <<<<<< VvS: here ?
                ipc_update_pid(&curr->sempid, q->pid);

Thank you,
	Vasily Averin
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Re: [PATCH] ipc: Remove dead code in perform_atomic_semop()

[Vasily Averin]

On 5/25/22 02:12, vasily.averin@linux.dev wrote:
> On 5/24/22 21:22, Gautam Menghani wrote:
>> Remove the line which is dead code. Fixes the clang scan warning:
>> warning: Value stored to 'result' is never read [deadcode.DeadStores]
>>                 result = curr->semval;
>>
>> Signed-off-by: Gautam Menghani <gautammenghani201@gmail.com>
>> ---
>>  ipc/sem.c | 1 -
>>  1 file changed, 1 deletion(-)
>>
>> diff --git a/ipc/sem.c b/ipc/sem.c
>> index 0dbdb98fdf2d..156824bcda47 100644
>> --- a/ipc/sem.c
>> +++ b/ipc/sem.c
>> @@ -766,7 +766,6 @@ static int perform_atomic_semop(struct sem_array *sma, struct sem_queue *q)
>>  	for (sop = sops; sop < sops + nsops; sop++) {
>>  		curr = &sma->sems[sop->sem_num];
>>  		sem_op = sop->sem_op;
>> -		result = curr->semval;
>>  
>>  		if (sop->sem_flg & SEM_UNDO) {
>>  			int undo = un->semadj[sop->sem_num] - sem_op;
> 
> Perhaps it would be better to keep the "result" but use it in the
> marked line below, like it was done in previous part of this function?

Sorry, I was wrong.
Reviewed-by: Vasily Averin <vvs@openvz.org>
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Re: [PATCH] ipc: Remove dead code in perform_atomic_semop()

[Manfred Spraul]

On 5/24/22 20:22, Gautam Menghani wrote:
> Remove the line which is dead code. Fixes the clang scan warning:
> warning: Value stored to 'result' is never read [deadcode.DeadStores]
>                  result = curr->semval;
>
> Signed-off-by: Gautam Menghani <gautammenghani201@gmail.com>
Reviewed-by: Manfred Spraul <manfred@colorfullife.com>
> ---
>   ipc/sem.c | 1 -
>   1 file changed, 1 deletion(-)
>
> diff --git a/ipc/sem.c b/ipc/sem.c
> index 0dbdb98fdf2d..156824bcda47 100644
> --- a/ipc/sem.c
> +++ b/ipc/sem.c
> @@ -766,7 +766,6 @@ static int perform_atomic_semop(struct sem_array *sma, struct sem_queue *q)
>   	for (sop = sops; sop < sops + nsops; sop++) {
>   		curr = &sma->sems[sop->sem_num];
>   		sem_op = sop->sem_op;
> -		result = curr->semval;
>   

A copy/paste mistake: The 1st loop in perform_atomic_semop() needs 
result - because it must check for overflows.

The 2nd loop doesn't need it.

>   		if (sop->sem_flg & SEM_UNDO) {
>   			int undo = un->semadj[sop->sem_num] - sem_op;

--

     Manfred

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