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Commit bb1256a7 authored by Mark Salyzyn's avatar Mark Salyzyn
Browse files

llkd: add bit_wait_io to stack monitoring 

This will discover if the I/O is starved.

Add the ability to search for " <symbol>.cfi+0x".

Cleaned up README.md to reflect current defaults.

Test: none
Bug: 113648929
Change-Id: I990a54f99de536406fd752a490e60f962380d71a
parent 31233916

llkd/README.md

+11 −7
Original line number Diff line number Diff line
@@ -44,7 +44,8 @@ then have a confirmed live-lock condition and need to panic. There is no 
ABA detection since forward scheduling progress is allowed, thus the condition

for the symbols are:



- Check is looking for " " + __symbol__+ "0x" in /proc/<pid>/stack.

- Check is looking for " __symbol__+0x" or " __symbol__.cfi+0x" in

  /proc/__pid__/stack.

- The __symbol__ should be rare and short lived enough that on a typical

  system the function is seen at most only once in a sample over the timeout

  period of ro.llk.stack.timeout_ms, samples occur every ro.llk.check_ms. This
@@ -121,14 +122,14 @@ default ro.llk.timeout_ms, Z maximum timelimit. 
#### ro.llk.stack.timeout_ms

default ro.llk.timeout_ms,

checking for persistent stack symbols maximum timelimit.

Only active on userdebug and eng builds.

Only active on userdebug or eng builds.



#### ro.llk.check_ms

default 2 minutes samples of threads for D or Z.



#### ro.llk.stack

default cma_alloc,__get_user_pages, comma separated list of kernel symbols.

The string "*false*" is the equivalent to an *empty* list.

default cma_alloc,__get_user_pages,bit_wait_io comma separated list of kernel

symbols.  The string "*false*" is the equivalent to an *empty* list.

Look for kernel stack symbols that if ever persistently present can

indicate a subsystem is locked up.

Beware, check does not on purpose do forward scheduling ABA except by polling
@@ -136,11 +137,14 @@ every ro.llk_check_ms over the period ro.llk.stack.timeout_ms, so stack symbol 
should be exceptionally rare and fleeting.

One must be convinced that it is virtually *impossible* for symbol to show up

persistently in all samples of the stack.

Only active on userdebug and eng builds.

Again, looks for a match for either " **symbol**+0x" or " **symbol**.cfi+0x"

in stack expansion.

Only available on userdebug or eng builds, limited privileges due to security

concerns on user builds prevents this checking.



#### ro.llk.blacklist.process

default 0,1,2 (kernel, init and [kthreadd]) plus process names

init,[kthreadd],[khungtaskd],lmkd,lmkd.llkd,llkd,watchdogd,

init,[kthreadd],[khungtaskd],lmkd,llkd,watchdogd,

[watchdogd],[watchdogd/0],...,[watchdogd/***get_nprocs**-1*].

The string "*false*" is the equivalent to an *empty* list.

Do not watch these processes.  A process can be comm, cmdline or pid reference.
@@ -160,7 +164,7 @@ The string "*false*" is the equivalent to an *empty* list. 
Do not watch processes that match this uid.



#### ro.llk.blacklist.process.stack

default process names init,lmkd,lmkd.llkd,llkd,keystore,logd.

default process names init,lmkd.llkd,llkd,keystore,ueventd,apexd,logd.

The string "*false*" is the equivalent to an *empty* list.

This subset of processes are not monitored for live lock stack signatures.

Also prevents the sepolicy violation associated with processes that block

llkd/include/llkd.h

+1 −1
Original line number Diff line number Diff line
@@ -48,7 +48,7 @@ unsigned llkCheckMilliseconds(void); 
/* LLK_CHECK_MS_DEFAULT = actual timeout_ms / LLK_CHECKS_PER_TIMEOUT_DEFAULT */

#define LLK_CHECKS_PER_TIMEOUT_DEFAULT 5

#define LLK_CHECK_STACK_PROPERTY       "ro.llk.stack"

#define LLK_CHECK_STACK_DEFAULT        "cma_alloc,__get_user_pages"

#define LLK_CHECK_STACK_DEFAULT        "cma_alloc,__get_user_pages,bit_wait_io"

#define LLK_BLACKLIST_PROCESS_PROPERTY "ro.llk.blacklist.process"

#define LLK_BLACKLIST_PROCESS_DEFAULT  \

    "0,1,2,init,[kthreadd],[khungtaskd],lmkd,llkd,watchdogd,[watchdogd],[watchdogd/0]"

llkd/libllkd.cpp

+2 −1
Original line number Diff line number Diff line
@@ -726,7 +726,8 @@ bool llkCheckStack(proc* procp, const std::string& piddir) { 
    char match = -1;

    for (const auto& stack : llkCheckStackSymbols) {

        if (++idx < 0) break;

        if (kernel_stack.find(" "s + stack + "+0x") != std::string::npos) {

        if ((kernel_stack.find(" "s + stack + "+0x") != std::string::npos) ||

            (kernel_stack.find(" "s + stack + ".cfi+0x") != std::string::npos)) {

            match = idx;

            break;

        }