Messages in this thread | | | Date | Mon, 14 Apr 2003 03:07:51 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH] 2.4.21-pre7 ide request races |
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Jens Axboe <axboe@suse.de> wrote: > > We've had some problems with request corruption on IDE in the past, IBM > traced these to stack corruption. In various places, the IDE code does > something ala: > > submission: > struct request rq; > > ... > ide_do_drive_cmd(drive, &rq, ide_wait); > > ide_end_request: > ... > blkdev_release_request() > > which works fine, as long as the stack persists for the > blkdev_release_request() call, but it may not if the task has already > exited (CPU0 may be waiting in ide_do_drive_cmd(), CPU1 gets the > completion interrupt, task is woken, and exits, CPU0 now calls > blkdev_release_request()). The result is random stack corruption (or > request list corruption, rq->q may have been scrippled!), not good. >
Those locally allocated requests are foul, and the patch is a good cleanup, but is a simpler fix more appropriate?
The bug is in end_that_request_last(), yes?
void end_that_request_last(struct request *req) { if (req->waiting != NULL) complete(req->waiting); req_finished_io(req);
blkdev_release_request(req); }
Wouldn't it be simpler to just do:
void end_that_request_last(struct request *req) { struct completion *c = req->waiting;
req_finished_io(req); blkdev_release_request(req); if (c) complete(c); }
I vaguely seem to remember being told months ago why this wasn't right ;)
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