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xtensa: add missing exclusive access state management 

The result of the s32ex opcode is recorded in the ATOMCTL special
register and must be retrieved with the getex opcode. Context switch
between s32ex and getex may trash the ATOMCTL register and result in
duplicate update or missing update of the atomic variable.
Add atomctl8 field to the struct thread_info and use getex to swap
ATOMCTL bit 8 as a part of context switch.
Clear exclusive access monitor on kernel entry.

Cc: stable@vger.kernel.org
Fixes: f7c34874f0 ("xtensa: add exclusive atomics support")
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
zero-sugar-mainline-defconfig
Max Filippov 2020-07-31 12:38:05 -07:00
parent 6d65d3769d
commit a0fc1436f1
3 changed files with 18 additions and 0 deletions
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4
arch/xtensa/include/asm/thread_info.h
View File

@ -55,6 +55,10 @@ struct thread_info {
mm_segment_t addr_limit; /* thread address space */
unsigned long cpenable;
#if XCHAL_HAVE_EXCLUSIVE
/* result of the most recent exclusive store */
unsigned long atomctl8;
#endif
/* Allocate storage for extra user states and coprocessor states. */
#if XTENSA_HAVE_COPROCESSORS

3
arch/xtensa/kernel/asm-offsets.c
View File

@ -93,6 +93,9 @@ int main(void)
DEFINE(THREAD_RA, offsetof (struct task_struct, thread.ra));
DEFINE(THREAD_SP, offsetof (struct task_struct, thread.sp));
DEFINE(THREAD_CPENABLE, offsetof (struct thread_info, cpenable));
#if XCHAL_HAVE_EXCLUSIVE
DEFINE(THREAD_ATOMCTL8, offsetof (struct thread_info, atomctl8));
#endif
#if XTENSA_HAVE_COPROCESSORS
DEFINE(THREAD_XTREGS_CP0, offsetof(struct thread_info, xtregs_cp.cp0));
DEFINE(THREAD_XTREGS_CP1, offsetof(struct thread_info, xtregs_cp.cp1));

11
arch/xtensa/kernel/entry.S
View File

@ -374,6 +374,11 @@ common_exception:
s32i a2, a1, PT_LCOUNT
#endif
#if XCHAL_HAVE_EXCLUSIVE
/* Clear exclusive access monitor set by interrupted code */
clrex
#endif
/* It is now save to restore the EXC_TABLE_FIXUP variable. */
rsr a2, exccause
@ -2020,6 +2025,12 @@ ENTRY(_switch_to)
s32i a3, a4, THREAD_CPENABLE
#endif
#if XCHAL_HAVE_EXCLUSIVE
l32i a3, a5, THREAD_ATOMCTL8
getex a3
s32i a3, a4, THREAD_ATOMCTL8
#endif
/* Flush register file. */
spill_registers_kernel