diff options
| author | Breno Leitao <leitao@debian.org> | 2018-11-08 15:12:42 -0200 |
|---|---|---|
| committer | Michael Ellerman <mpe@ellerman.id.au> | 2018-12-04 19:45:01 +1100 |
| commit | 8d4a862276a9c30a269d368d324fb56529e6d5fd (patch) | |
| tree | a2adc5809a07776554d7be9215cd93f4b72e5f60 | |
| parent | 26598f2856e91533af40ba8d05c7c4a8a0300e37 (diff) | |
| download | linux-8d4a862276a9c30a269d368d324fb56529e6d5fd.tar.bz2 | |
powerpc/xmon: Fix invocation inside lock region
Currently xmon needs to get devtree_lock (through rtas_token()) during its
invocation (at crash time). If there is a crash while devtree_lock is being
held, then xmon tries to get the lock but spins forever and never get into
the interactive debugger, as in the following case:
int *ptr = NULL;
raw_spin_lock_irqsave(&devtree_lock, flags);
*ptr = 0xdeadbeef;
This patch avoids calling rtas_token(), thus trying to get the same lock,
at crash time. This new mechanism proposes getting the token at
initialization time (xmon_init()) and just consuming it at crash time.
This would allow xmon to be possible invoked independent of devtree_lock
being held or not.
Signed-off-by: Breno Leitao <leitao@debian.org>
Reviewed-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
| -rw-r--r-- | arch/powerpc/xmon/xmon.c | 18 |
1 files changed, 14 insertions, 4 deletions
diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c index 1e718431ac1c..1f943e884e85 100644 --- a/arch/powerpc/xmon/xmon.c +++ b/arch/powerpc/xmon/xmon.c @@ -75,6 +75,9 @@ static int xmon_gate; #define xmon_owner 0 #endif /* CONFIG_SMP */ +#ifdef CONFIG_PPC_PSERIES +static int set_indicator_token = RTAS_UNKNOWN_SERVICE; +#endif static unsigned long in_xmon __read_mostly = 0; static int xmon_on = IS_ENABLED(CONFIG_XMON_DEFAULT); @@ -358,7 +361,6 @@ static inline void disable_surveillance(void) #ifdef CONFIG_PPC_PSERIES /* Since this can't be a module, args should end up below 4GB. */ static struct rtas_args args; - int token; /* * At this point we have got all the cpus we can into @@ -367,11 +369,11 @@ static inline void disable_surveillance(void) * If we did try to take rtas.lock there would be a * real possibility of deadlock. */ - token = rtas_token("set-indicator"); - if (token == RTAS_UNKNOWN_SERVICE) + if (set_indicator_token == RTAS_UNKNOWN_SERVICE) return; - rtas_call_unlocked(&args, token, 3, 1, NULL, SURVEILLANCE_TOKEN, 0, 0); + rtas_call_unlocked(&args, set_indicator_token, 3, 1, NULL, + SURVEILLANCE_TOKEN, 0, 0); #endif /* CONFIG_PPC_PSERIES */ } @@ -3688,6 +3690,14 @@ static void xmon_init(int enable) __debugger_iabr_match = xmon_iabr_match; __debugger_break_match = xmon_break_match; __debugger_fault_handler = xmon_fault_handler; + +#ifdef CONFIG_PPC_PSERIES + /* + * Get the token here to avoid trying to get a lock + * during the crash, causing a deadlock. + */ + set_indicator_token = rtas_token("set-indicator"); +#endif } else { __debugger = NULL; __debugger_ipi = NULL; |