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| author |   Leonardo Bras <leobras.c@gmail.com> | 2020-05-18 20:42:45 -0300 |
|---|---|---|
| committer |   Michael Ellerman <mpe@ellerman.id.au> | 2020-06-02 20:59:08 +1000 |
| commit | b664db8e3f976d9233cc9ea5e3f8a8c0bcabeb48 (patch) | |
| tree | 487ddb1404c7fd3029a5e72167fa4010d7ef002e /arch/powerpc/include/asm/paca.h | |
| parent | powerpc/rtas: Move type/struct definitions from rtas.h into rtas-types.h (diff) | |
| download | linux-dev-b664db8e3f976d9233cc9ea5e3f8a8c0bcabeb48.tar.xz linux-dev-b664db8e3f976d9233cc9ea5e3f8a8c0bcabeb48.zip | |
powerpc/rtas: Implement reentrant rtas call
Implement rtas_call_reentrant() for reentrant rtas-calls:
"ibm,int-on", "ibm,int-off",ibm,get-xive" and "ibm,set-xive".
On LoPAPR Version 1.1 (March 24, 2016), from 7.3.10.1 to 7.3.10.4,
items 2 and 3 say:
2 - For the PowerPC External Interrupt option: The * call must be
reentrant to the number of processors on the platform.
3 - For the PowerPC External Interrupt option: The * argument call
buffer for each simultaneous call must be physically unique.
So, these rtas-calls can be called in a lockless way, if using
a different buffer for each cpu doing such rtas call.
For this, it was suggested to add the buffer (struct rtas_args)
in the PACA struct, so each cpu can have it's own buffer.
The PACA struct received a pointer to rtas buffer, which is
allocated in the memory range available to rtas 32-bit.
Reentrant rtas calls are useful to avoid deadlocks in crashing,
where rtas-calls are needed, but some other thread crashed holding
the rtas.lock.
This is a backtrace of a deadlock from a kdump testing environment:
#0 arch_spin_lock
#1 lock_rtas ()
#2 rtas_call (token=8204, nargs=1, nret=1, outputs=0x0)
#3 ics_rtas_mask_real_irq (hw_irq=4100)
#4 machine_kexec_mask_interrupts
#5 default_machine_crash_shutdown
#6 machine_crash_shutdown
#7 __crash_kexec
#8 crash_kexec
#9 oops_end
Signed-off-by: Leonardo Bras <leobras.c@gmail.com>
[mpe: Move under #ifdef PSERIES to avoid build breakage]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200518234245.200672-3-leobras.c@gmail.com
Diffstat (limited to 'arch/powerpc/include/asm/paca.h')
| -rw-r--r-- | arch/powerpc/include/asm/paca.h | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/arch/powerpc/include/asm/paca.h b/arch/powerpc/include/asm/paca.h index e3cc9eb9204d..45a839a7c6cf 100644 --- a/arch/powerpc/include/asm/paca.h +++ b/arch/powerpc/include/asm/paca.h @@ -29,6 +29,7 @@ #include <asm/hmi.h> #include <asm/cpuidle.h> #include <asm/atomic.h> +#include <asm/rtas-types.h> #include <asm-generic/mmiowb_types.h> @@ -256,6 +257,7 @@ struct paca_struct { u64 l1d_flush_size; #endif #ifdef CONFIG_PPC_PSERIES + struct rtas_args *rtas_args_reentrant; u8 *mce_data_buf; /* buffer to hold per cpu rtas errlog */ #endif /* CONFIG_PPC_PSERIES */ |