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| author | Catalin Marinas <catalin.marinas@arm.com> | 2009-09-19 02:27:05 +0400 |
|---|---|---|
| committer | Catalin Marinas <catalin.marinas@arm.com> | 2009-09-19 02:30:11 +0400 |
| commit | 200b812d0084f800bc52465e273b118ff5f8141f (patch) | |
| tree | 6dbef78960ad7b83a76df064751275913583068c /arch/arm/kernel/entry-header.S | |
| parent | df58bee21ed218cb7dfb561a590b1bd2a99531cf (diff) | |
| download | linux-200b812d0084f800bc52465e273b118ff5f8141f.tar.xz | |
Clear the exclusive monitor when returning from an exception
The patch adds a CLREX or dummy STREX to the exception return path. This
is needed because several atomic/locking operations use a pair of
LDREX/STREXEQ and the EQ condition may not always be satisfied. This
would leave the exclusive monitor status set and may cause problems with
atomic/locking operations in the interrupted code.
With this patch, the atomic_set() operation can be a simple STR
instruction (on SMP systems, the global exclusive monitor is cleared by
STR anyway). Clearing the exclusive monitor during context switch is no
longer needed as this is handled by the exception return path anyway.
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Reported-by: Jamie Lokier <jamie@shareable.org>
Diffstat (limited to 'arch/arm/kernel/entry-header.S')
| -rw-r--r-- | arch/arm/kernel/entry-header.S | 14 |
1 files changed, 14 insertions, 0 deletions
diff --git a/arch/arm/kernel/entry-header.S b/arch/arm/kernel/entry-header.S index a4eaf4f920c5..e17e3c30d957 100644 --- a/arch/arm/kernel/entry-header.S +++ b/arch/arm/kernel/entry-header.S @@ -76,13 +76,25 @@ #ifndef CONFIG_THUMB2_KERNEL .macro svc_exit, rpsr msr spsr_cxsf, \rpsr +#if defined(CONFIG_CPU_32v6K) + clrex @ clear the exclusive monitor ldmia sp, {r0 - pc}^ @ load r0 - pc, cpsr +#elif defined (CONFIG_CPU_V6) + ldr r0, [sp] + strex r1, r2, [sp] @ clear the exclusive monitor + ldmib sp, {r1 - pc}^ @ load r1 - pc, cpsr +#endif .endm .macro restore_user_regs, fast = 0, offset = 0 ldr r1, [sp, #\offset + S_PSR] @ get calling cpsr ldr lr, [sp, #\offset + S_PC]! @ get pc msr spsr_cxsf, r1 @ save in spsr_svc +#if defined(CONFIG_CPU_32v6K) + clrex @ clear the exclusive monitor +#elif defined (CONFIG_CPU_V6) + strex r1, r2, [sp] @ clear the exclusive monitor +#endif .if \fast ldmdb sp, {r1 - lr}^ @ get calling r1 - lr .else @@ -98,6 +110,7 @@ .endm #else /* CONFIG_THUMB2_KERNEL */ .macro svc_exit, rpsr + clrex @ clear the exclusive monitor ldr r0, [sp, #S_SP] @ top of the stack ldr r1, [sp, #S_PC] @ return address tst r0, #4 @ orig stack 8-byte aligned? @@ -110,6 +123,7 @@ .endm .macro restore_user_regs, fast = 0, offset = 0 + clrex @ clear the exclusive monitor mov r2, sp load_user_sp_lr r2, r3, \offset + S_SP @ calling sp, lr ldr r1, [sp, #\offset + S_PSR] @ get calling cpsr |