Re: [PATCH v2] Bluetooth: vhci, fix open_timeout vs. hdev race

From	Jiri Slaby <jslaby@suse.cz>
Newsgroups	linux.kernel
Subject	Re: [PATCH v2] Bluetooth: vhci, fix open_timeout vs. hdev race
Date	2016-03-22 17:00 +0100
Message-ID	<rfwSS-6Bo-9@gated-at.bofh.it> (permalink)
References	<relG9-6qO-7@gated-at.bofh.it> <relZv-6PZ-11@gated-at.bofh.it> <rfvar-5AR-19@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On 03/22/2016, 03:00 PM, Takashi Iwai wrote:
> int main()
> {
> 	int i;
> 	long fd;
>         pthread_t th[32];
> 
> 	fd = open("/dev/vhci", O_RDWR);
> 	if (fd < 0)
> 		err(1, "open");
>         for (i = 0; i < 32; i++)
> 		pthread_create(&th[i], 0, test, (void*)fd);
>         for (i = 0; i < 32; i++)
> 		pthread_join(th[i], NULL);
> 	return 0;
> }
> ================================================================
> 
> For fixing these, we need a proper mutex protection.  A patch like
> below seems helping, at least for the test case above.

I didn't fix this and kept it simple as I believe concurrent accesses
from a single opener are not allowed by design. But if we want to
support this, we of course need locking like this.

Anyway, I would appreciate any input from the BT fellows. There are more
races like this, apparently.

thanks,
-- 
js
suse labs

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[PATCH] Bluetooth: vhci, fix open_timeout vs. hdev race Jiri Slaby <jslaby@suse.cz> - 2016-03-19 10:50 +0100
  [PATCH v2] Bluetooth: vhci, fix open_timeout vs. hdev race Jiri Slaby <jslaby@suse.cz> - 2016-03-19 11:10 +0100
    Re: [PATCH v2] Bluetooth: vhci, fix open_timeout vs. hdev race Takashi Iwai <tiwai@suse.de> - 2016-03-22 15:10 +0100
      Re: [PATCH v2] Bluetooth: vhci, fix open_timeout vs. hdev race Jiri Slaby <jslaby@suse.cz> - 2016-03-22 17:00 +0100

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