Messages in this thread | | | Date | Mon, 14 Jul 2014 13:08:39 +0100 | From | Catalin Marinas <> | Subject | Re: [PATCH v2] ARM: Fix preemption disable in iwmmxt_task_enable() |
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On Sat, Jul 12, 2014 at 12:05:30PM +0100, Sebastian Hesselbarth wrote: > commit 431a84b1a4f7d1a0085d5b91330c5053cc8e8b12 > ("ARM: 8034/1: Disable preemption in iwmmxt_task_enable()") > introduced macros {inc,dec}_preempt_count to iwmmxt_task_enable > to make it run with preemption disabled. > > Unfortunately, other functions in iwmmxt.S also use concan_{save,dump,load} > sections located in iwmmxt_task_enable() to deal with iWMMXt coprocessor. > This causes an unbalanced preempt_count due to excessive dec_preempt_count > and destroyed return addresses in callers of concan_ labels due to a register > collision: > > Linux version 3.16.0-rc3-00062-gd92a333-dirty (jef@armhf) (gcc version 4.8.3 (Debian 4.8.3-4) ) #5 PREEMPT Thu Jul 3 19:46:39 CEST 2014 > CPU: ARMv7 Processor [560f5815] revision 5 (ARMv7), cr=10c5387d > CPU: PIPT / VIPT nonaliasing data cache, PIPT instruction cache > Machine model: SolidRun CuBox > ... > PJ4 iWMMXt v2 coprocessor enabled. > ... > Unable to handle kernel paging request at virtual address fffffffe > pgd = bb25c000 > [fffffffe] *pgd=3bfde821, *pte=00000000, *ppte=00000000 > Internal error: Oops: 80000007 [#1] PREEMPT ARM > Modules linked in: > CPU: 0 PID: 62 Comm: startpar Not tainted 3.16.0-rc3-00062-gd92a333-dirty #5 > task: bb230b80 ti: bb256000 task.ti: bb256000 > PC is at 0xfffffffe > LR is at iwmmxt_task_copy+0x44/0x4c > pc : [<fffffffe>] lr : [<800130ac>] psr: 40000033 > sp : bb257de8 ip : 00000013 fp : bb257ea4 > r10: bb256000 r9 : fffffdfe r8 : 76e898e6 > r7 : bb257ec8 r6 : bb256000 r5 : 7ea12760 r4 : 000000a0 > r3 : ffffffff r2 : 00000003 r1 : bb257df8 r0 : 00000000 > Flags: nZcv IRQs on FIQs on Mode SVC_32 ISA Thumb Segment user > Control: 10c5387d Table: 3b25c019 DAC: 00000015 > Process startpar (pid: 62, stack limit = 0xbb256248) > > This patch fixes the issue by moving concan_{save,dump,load} into separate > code sections and make iwmmxt_task_enable() call them in the same way the > other functions use concan_ symbols. The test for valid ownership is moved > to concan_save and is safe for the other user of it, iwmmxt_task_disable(). > The register collision is also resolved by moving concan_ symbols as > {inc,dec}_preempt_count are now local to iwmmxt_task_enable(). > > Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com> > Reported-by: Jean-Francois Moine <moinejf@free.fr> > Fixes: 431a84b1a4f7 ("ARM: 8034/1: Disable preemption in iwmmxt_task_enable()") > --- > The offending commit was intoduced past v3.15-rc1 and the corresponding fix > should also be queued up for stable v3.15+ > > Changelog > v1->v2: > - return immediately from concan_ instead of branch to 3f, i.e. replace > 'beq 3f' with 'moveq pc, lr' (Suggested by Catalin Marinas) > > Cc: Russell King <linux@arm.linux.org.uk> > Cc: Catalin Marinas <catalin.marinas@arm.com> > Cc: Jean-Francois Moine <moinejf@free.fr> > Cc: Jason Cooper <jason@lakedaemon.net> > Cc: linux-arm-kernel@lists.infradead.org > Cc: linux-kernel@vger.kernel.org
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
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