> On 30 Jul 2016, at 11:50, Johannes Sixt <j6t@xxxxxxxx> wrote:
>
> Am 30.07.2016 um 01:37 schrieb larsxschneider@xxxxxxxxx:
>> Some commands might need to perform cleanup tasks on exit. Let's give
>> them an interface for doing this.
>>
>> Signed-off-by: Lars Schneider <larsxschneider@xxxxxxxxx>
>> ---
>> run-command.c | 12 ++++++++----
>> run-command.h | 1 +
>> 2 files changed, 9 insertions(+), 4 deletions(-)
>>
>> diff --git a/run-command.c b/run-command.c
>> index 33bc63a..197b534 100644
>> --- a/run-command.c
>> +++ b/run-command.c
>> @@ -21,6 +21,7 @@ void child_process_clear(struct child_process *child)
>>
>> struct child_to_clean {
>> pid_t pid;
>> + void (*clean_on_exit_handler)(pid_t);
>> struct child_to_clean *next;
>> };
>> static struct child_to_clean *children_to_clean;
>> @@ -30,6 +31,8 @@ static void cleanup_children(int sig, int in_signal)
>> {
>> while (children_to_clean) {
>> struct child_to_clean *p = children_to_clean;
>> + if (p->clean_on_exit_handler)
>> + p->clean_on_exit_handler(p->pid);
>
> This summons demons. cleanup_children() is invoked from a signal handler. In this case, it can call only async-signal-safe functions. It does not look like the handler that you are going to install later will take note of this caveat!
>
>> children_to_clean = p->next;
>> kill(p->pid, sig);
>> if (!in_signal)
>
> The condition that we see here in the context protects free(p) (which is not async-signal-safe). Perhaps the invocation of the new callback should be skipped in the same manner when this is called from a signal handler? 507d7804 (pager: don't use unsafe functions in signal handlers) may be worth a look.
Thanks a lot of pointing this out to me!
Do I get it right that after the signal "SIGTERM" I can do a cleanup and don't
need to worry about any function calls but if I get any other signal then I can
only perform async-signal-safe calls?
If this is correct, then the following solution would work great:
if (!in_signal && p->clean_on_exit_handler)
p->clean_on_exit_handler(p->pid);
Thanks,
Lars--
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