Messages in this thread | | | Subject | Re: [PATCH] hysdn: fix to a race condition in put_log_buffer | From | Sergei Shtylyov <> | Date | Thu, 3 Aug 2017 15:03:13 +0300 |
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Hello!
On 08/03/2017 02:33 PM, Anton Volkov wrote:
> The synchronization type that was used earlier to guard the loop that > deletes unused log buffers may lead to a situation that prevents any > thread from going through the loop. > > The patch deletes previously used synchronization mechanism and moves > the loop under the spin_lock so the similar cases won't be feasible in > the future. > > Found by by Linux Driver Verification project (linuxtesting.org). > > Signed-off-by: Anton Volkov <avolkov@ispras.ru> > --- > drivers/isdn/hysdn/hysdn_proclog.c | 27 ++++++++++++--------------- > 1 file changed, 12 insertions(+), 15 deletions(-) > > diff --git a/drivers/isdn/hysdn/hysdn_proclog.c b/drivers/isdn/hysdn/hysdn_proclog.c > index 7b5fd8f..b152c6c 100644 > --- a/drivers/isdn/hysdn/hysdn_proclog.c > +++ b/drivers/isdn/hysdn/hysdn_proclog.c [...] > else > pd->log_tail->next = ib; /* follows existing messages */ > pd->log_tail = ib; /* new tail */ > - i = pd->del_lock++; /* get lock state */ > - spin_unlock_irqrestore(&card->hysdn_lock, flags); > > /* delete old entrys */ > - if (!i) > - while (pd->log_head->next) { > - if ((pd->log_head->usage_cnt <= 0) && > - (pd->log_head->next->usage_cnt <= 0)) { > - ib = pd->log_head; > - pd->log_head = pd->log_head->next; > - kfree(ib); > - } else > - break; > - } /* pd->log_head->next */ > - pd->del_lock--; /* release lock level */ > + while (pd->log_head->next) { > + if ((pd->log_head->usage_cnt <= 0) && > + (pd->log_head->next->usage_cnt <= 0)) { > + ib = pd->log_head; > + pd->log_head = pd->log_head->next; > + kfree(ib); > + } else > + break; > + } /* pd->log_head->next */
Need {} in the *else* branch as *if* had them.
[...]
MBR, Sergei
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