On Sat, Apr 20, 2013 at 10:00 PM, Davidlohr Bueso <davidlohr.bueso@xxxxxx> wrote: > On Sat, 2013-04-20 at 02:19 +0200, Sedat Dilek wrote: >> On Sat, Apr 20, 2013 at 2:06 AM, Sedat Dilek <sedat.dilek@xxxxxxxxx> wrote: >> > On Sat, Apr 20, 2013 at 1:02 AM, Linus Torvalds >> > <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote: >> >> On Fri, Apr 19, 2013 at 3:55 PM, Sedat Dilek <sedat.dilek@xxxxxxxxx> wrote: >> >>> >> >>> Davidlohr pointed to this patch (tested the triplet): >> >>> >> >>> ipc, sem: do not call sem_lock when bogus sma: >> >>> https://lkml.org/lkml/2013/3/31/12 >> >>> >> >>> Is that what you mean? >> >> >> >> Yup. >> >> >> > >> > Davidlohr Bueso (1): >> > ipc, sem: do not call sem_lock when bogus sma >> > >> > Linus Torvalds (1): >> > crazy rcu double free debug hack >> > >> > With ***both*** patches applied I am able to build a Linux-kernel with >> > 4 parallel-make-jobs again. >> > David's or your patch alone are not sufficient! >> > >> >> [ Still both patches applied ] >> >> To correct myself... The 1st run was OK. >> >> The 2nd run shows a NULL-pointer-deref (excerpt): >> >> [ 178.490583] BUG: spinlock bad magic on CPU#1, sh/8066 >> [ 178.490595] lock: 0xffff88008b53ea18, .magic: 6b6b6b6b, .owner: >> make/8068, .owner_cpu: 3 >> [ 178.490599] BUG: unable to handle kernel NULL pointer dereference >> at (null) >> [ 178.490608] IP: [<ffffffff812bacd0>] update_queue+0x70/0x210 >> [ 178.490610] PGD 0 >> [ 178.490612] Oops: 0000 [#1] SMP >> ... > > The exit_sem() >> do_smart_update() >> update_queue() calls seem pretty > well protected. Furthermore we're asserting that sma->sem_perm.lock is > taken. This could just be a consequence of another issue. Earlier this > week Andrew pointed out a potential race in semctl_main() where > sma->sem_perm.deleted could be changed when cmd == GETALL. > > Sedat, could you try the attached patch to keep the ipc lock acquired > (on top of the three patches you're already using) and let us know how > it goes? We could also just have the RCU read lock instead of > ->sem.perm.lock for GETALL, but lets play it safe for now. > I had to refresh your patch and it contain strange ^M charachters as well. NOPE, the machine gets FROZEN (cold reboot). - Sedat - P.S.: I have attached all 4 patches against next-20130419 in case someone wants to follow. > Thanks, > Davidlohr >
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0001-ipc-sem-untangle-RCU-locking-with-find_alloc_undo.patch
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0002-ipc-sem-fix-lockdep-false-positive.patch
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0003-ipc-sem-do-not-call-sem_lock-when-bogus-sma.patch
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0004-ipc-sem-check-if-the-ipc-lock-has-been-already-taken.patch
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