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infra: fix race on deletion of say channels

This commit is contained in:
Thomas Schoebel-Theuer 2013-04-24 10:45:08 +02:00
parent 8d93439dcb
commit 803a1c8419
1 changed files with 28 additions and 4 deletions
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32
kernel/brick_say.c
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@ -81,6 +81,7 @@ struct say_channel {
bool ch_rollover;
bool ch_must_exist;
bool ch_is_dir;
bool ch_delete;
int ch_status_written;
int ch_id_max;
void *ch_ids[MAX_IDS];
@ -248,6 +249,20 @@ void rollover_all(void)
EXPORT_SYMBOL_GPL(rollover_all);
void del_channel(struct say_channel *ch)
{
if (unlikely(!ch))
return;
if (unlikely(ch == default_channel)) {
say_to(default_channel, SAY_ERROR, "thread '%s' tried to delete the default channel\n", current->comm);
return;
}
ch->ch_delete = true;
}
EXPORT_SYMBOL_GPL(del_channel);
static
void _del_channel(struct say_channel *ch)
{
struct say_channel *tmp;
struct say_channel **_tmp;
@ -269,6 +284,7 @@ void del_channel(struct say_channel *ch)
for (j = 0; j < 2; j++) {
if (ch->ch_filp[i][j]) {
filp_close(ch->ch_filp[i][j], NULL);
ch->ch_filp[i][j] = NULL;
}
}
for (j = 0; j < 2; j++) {
@ -286,7 +302,6 @@ void del_channel(struct say_channel *ch)
kfree(ch);
atomic_dec(&say_alloc_channels);
}
EXPORT_SYMBOL_GPL(del_channel);
static
struct say_channel *_make_channel(const char *name, bool must_exist)
@ -372,7 +387,7 @@ struct say_channel *make_channel(const char *name, bool must_exist)
for (ch = channel_list; ch; ch = ch->ch_next) {
if (ch != res && unlikely(!strcmp(ch->ch_name, name))) {
del_channel(res);
_del_channel(res);
res = ch;
goto race_found;
}
@ -402,8 +417,12 @@ void _say(struct say_channel *ch, int class, va_list args, bool use_args, const
int rest;
int written;
if (!ch)
if (unlikely(!ch))
return;
if (unlikely(ch->ch_delete && ch != default_channel)) {
say_to(default_channel, SAY_ERROR, "thread '%s' tried to write on deleted channel\n", current->comm);
return;
}
offset = ch->ch_index[class];
start = ch->ch_buf[class][0] + offset;
@ -745,6 +764,11 @@ int _say_thread(void *data)
goto restart;
}
}
if (ch->ch_delete) {
read_unlock(&say_lock);
_del_channel(ch);
goto restart;
}
}
read_unlock(&say_lock);
}
@ -780,7 +804,7 @@ void exit_say(void)
default_channel = NULL;
while (channel_list) {
del_channel(channel_list);
_del_channel(channel_list);
}
memleak_channels = atomic_read(&say_alloc_channels);